Display and its driving method

ABSTRACT

An array substrate ( 10 ) is provided with a pixel electrode ( 3 ) disposed in a region defined by two adjacent gate wirings ( 1 ) and two adjacent source wirings ( 2 ), a switching element ( 5 ) for switching a voltage applied to the pixel electrode ( 3 ) from the source wiring ( 2 ) based on a signal voltage supplied from the gate wiring ( 1 ), a common wiring ( 8 ) arranged between the two adjacent gate wirings ( 1 ) and a common electrode ( 4 ) being electrically connected to the common wiring ( 8 ) and generating an electric field between the pixel electrode ( 3 ) whereto a voltage is applied, wherein the pixel electrode ( 1 ) comprises a first pixel electrode ( 1 a) and a second pixel electrode ( 2 a), and the opposing electrode ( 2 ) comprises a first opposing electrode ( 1 b) and a second opposing electrode ( 2 b), wherein a first region generates an electric field between the first pixel electrode ( 1 a) and the first opposing electrode ( 2 a) whose light transmittance is lower than that of the first pixel electrode ( 1 a) and a second region generates an electric field between the second pixel electrode ( 1 b) and the second opposing electrode ( 2 b) whose light transmittance is higher than that of the second pixel electrode ( 1 b) are formed.

TECHNICAL FIELD

[0001] The present invention relates to display devices such as liquidcrystal display devices, etc., and driving methods thereof.

BACKGROUND ART

[0002] Liquid crystal display devices are in wide use as thin and lightflat displays for use in various electronic machines. There are severaldisplay schemes used in liquid crystal display devices. Among those, ascheme known as IPS (In-Plane Switching), in which an electric field isapplied to liquid crystal in parallel to a substrate for obtaining awide viewing angle, is suitably used for monitor displays for use inpersonal computers, liquid crystal TV sets or the like because of itsexcellent image properties.

[0003] Liquid crystal display devices using IPS are disclosed inJapanese Unexamined Patent Publication No. 10-10556, for example. A planview of a pixel portion thereof is shown in FIG. 47. Such a liquidcrystal display device comprises an array substrate and an opposingsubstrate parallel to each other, and liquid crystal held between thearray substrate and the opposing substrate. As shown in FIG. 47, in thearray substrate, gate wirings 101 feeding scanning signals and sourcewirings 102 feeding image signals are arranged so as to intersect atapproximately right angles. Nearby each intersection of the gate wiring101 and the source wiring 102, a thin-film transistor (TFT) 104 having asemiconductor layer is formed as a switching element. To the sourcewiring 102, a comb-like pixel electrode 115 is connected via the TFT104. Opposing electrodes 116 functioning as a standard potential arearranged so as to mesh with the pixel electrode 115. The opposingelectrodes 116 are electrically connected to a common wiring 103parallel to the gate wiring 101 through a contact hole 108. At theintersection of the common wiring 103 and the pixel electrode 115, withan insulating layer (not shown) in between, a storage capacitor region107 is formed.

[0004] According to such a liquid crystal display device, an electricfield substantially parallel to the substrates is generated by thedifference between the voltage applied to the pixel electrode 115 andthat of the opposing electrode 116, to which a standard potential isapplied, and thereby the liquid crystal (not shown) held between theelectrodes is driven. By storing electric charge in the storagecapacitor region 107 while the TFT 104 is in an on-status, the liquidcrystal remains actuated while the TFT 104 is in an off-status.

[0005] In prior art IPS style liquid crystal display devices, pixelelectrodes and opposing electrodes are generally made of aluminum or thelike metals. Therefore, the pixel electrodes and opposing electrodes donot transmit light, leading to the drawback of an unsatisfactory pixelaperture ratio. Japanese Unexamined Patent Publication No. 10-10556proposes a way to enhance the aperture ratio by forming either or bothof the pixel electrode 115 and the opposing electrode 116 out of atransparent conductive film.

[0006] In the case where both the pixel electrode 115 and the opposingelectrode 116 are made of transparent electrodes, it is preferable thatboth the electrodes be formed as a same layer in order to avoid a morecomplicated production process and increased manufacturing costs.However, this arrangement may lower the manufacturing yield by causingshort-circuits between the pixel electrode 115 and the opposingelectrode 116. Therefore, it is more practical that either the pixelelectrode or the opposing electrode be made of a transparent electrode.

[0007] However, forming only one of the pixel electrode and the opposingelectrode out of a transparent electrode and forming the other out ofmetal or a like material may cause flicker due to the difference in theoptical properties of the two materials.

[0008] In order to apply a sufficient voltage to liquid crystalmolecules while preventing decomposition or deterioration thereof,liquid crystal display devices are driven by the alternating currentdrive method, where an electric potential alternately positive andnegative relative to that of the opposing electrode is applied to thepixel electrode at a regular interval (for example, once every sixtiethseconds). When the alternating current drive method is employed in aliquid crystal display device in which only one of the pixel electrodeand the opposing electrode is a transparent electrode, its transmittancechanges cyclically between the period when an electric potentialpositive relative to that of the opposing electrode (positive frame) isapplied to the pixel electrode and the period when an electric potentialnegative relative to that of the opposing electrode (negative frame) isapplied to the pixel electrode, causing observable differences inbrightness.

DISCLOSURE OF THE INVENTION

[0009] The present invention aims to overcome the drawbacks describedabove. An object of the invention is to prevent flicker of a displaydevice in which an electro-optic material is driven by applying avoltage between two electrodes having different transmittances.

[0010] The inventors conducted research into the causes of the flickerdescribed above and found that the following two factors greatly affectthe occurrence of flicker. A first factor is the flexoelectric effect.The flexoelectric effect is a polarization phenomenon brought about bysplay deformation (orientation deformation) of liquid crystal. Regardingthe relationship between the flexoelectric effect and IPS, “Manuscriptsof Lectures at the 1999 Japanese Liquid Crystal Conference” (page 514,lecture number 3D06) explains the occurrence of domain reversal inconnection with the positive and negative electrodes and rubbingdirection.

[0011] How the flexoelectric effect influences flicker will be explainedbelow with reference to FIGS. 44(a), 44(b), 44(c) and 44(d). In FIG.44(a), when a positive voltage is applied to an electrode 21 and anegative voltage is applied to an electrode 22 in a liquid crystaldisplay device using IPS or the like where a lateral electric field isapplied, a solid line 26 represents a line of electric force, when theshape effect of the liquid crystal molecules is left out ofconsideration. On the electrodes 21 and 22, the lines of electric forcesplay out. In this figure, 23 represents a liquid crystal layer, 24represents an opposing substrate, and 25 represents an array substrate.Liquid crystal display devices are driven by the alternating currentdrive method. Therefore, the direction of the electric field reverses,for example, once every sixtieth of seconds.

[0012]FIG. 44(b) shows an array of liquid crystal molecules 27 formedout of this splay electric field. To the end of each of the liquidcrystal molecules, a cyano group, a fluorine atom or the like isintroduced to give dielectric anisotropy. These parts function asnegative electrodes of a dipole moment and compose the larger part ofthe molecular skeleton. As shown in an enlarged view of FIG. 44(b) (inthe circle), the molecule has a wedge-like shape opening to the negativeelectrode side. Because of the shape effect (excluded volume effect),when a splay shape alternating electric field is applied to the liquidcrystal molecules, they will tend to be arranged so as to direct thenarrower end of the wedge to the electrode side and the wider end to thecenter of the liquid crystal layer. The liquid crystal molecules 27 areuniformly aligned as described above and this generates an electricfield 28 attributable to the liquid crystal molecules. This phenomenonis known as the flexoelectric effect.

[0013]FIG. 44(c) illustrates a composite electric field 29 shown bybroken lines which is generated by the original electric field 26 andthe electric field 28 attributable to the flexoelectric effect in theliquid crystal molecules. The composite electric field 29 exhibits astronger vertical electric field on the positive electrode 21 side and aweaker vertical electric field on the negative electrode 22 side.

[0014] As a result, its distribution of transmittance varies dependingon the polarity (i.e., positive or negative) of the applied voltage.FIG. 44(d) shows the transmittance distribution when both electrodes 21and 22 are transparent. Here, the solid line shows the transmittancedistribution when the electrode 21 has a positive electric potential(positive frame), and the dash-and-dot line shows the transmittancedistribution when the electrode 21 has a negative electric potential(negative frame). Both electrodes are symmetric with respect to alongitudinal axis passing through the midpoint thereof. Therefore, whenboth electrodes 21 and 22 are transparent or both electrodes 21 and 22have opaque properties, very little variance in the transmittancebetween the positive and negative frames is observed. When one of theelectrodes transmits light and the other blocks light or thetransmittances of the two electrodes 21 and 22 are significantlydifferent, the transmittance of the pixel differs between the positiveand negative frames due to the difference of their optical contributionratios, causing flicker.

[0015] A second main factor causing flicker is influence by a peripheralelectric potential. FIG. 45(a) shows equipotential lines when, out ofthe three electrodes 32, 33 and 34 disposed on an array substrate 36, avoltage of −5 volts (V) is applied to the end electrodes 32 and 34 and avoltage of +5 V is applied to the middle electrode 33. When the electricpotential of the interface of opposing substrate 35 is assumed to be theaverage of the two voltages (i.e. 0 V), equipotential lines of 0 V existon the lines normal to the substrate passing through points equidistantto any two adjacent electrodes among 32, 33 and 34. Therefore, when theflexoelectric effect is left out of consideration, the three electrodes32, 33 and 34 are equivalent. Therefore, when the electrode 33 has apositive electric potential and when it has a negative electricpotential, its transmittance distribution is shown by the solid line inFIG. 45(b), and this enables the transmittance of the pixel to remainstable, even when some of the plurality of electrodes 32, 33 and 34is/are made transparent, resulting in no occurrence of flicker.

[0016] However, in an IPS style liquid crystal display device, there isno electrode on the surface of the opposing substrate and this makes itdifficult to form a desirable electric potential on the interface 35.Therefore, if the electric potential of the interface 35 of the opposingsubstrate is assumed to be −5 V, in cases where the electrode 33 has apositive electric potential, as shown in FIG. 46(a), equipotential linesof −5 V form above electrodes 32 and 34 along the direction normal tothe substrate. In this case, the transmittance distribution is as shownby the solid line in FIG. 46(b), i.e., the transmittances on the end ofelectrodes (negative electrodes) 32 and 34 are higher than that on themiddle electrode (positive electrode) 33. On the other hand, when theelectrode 33 has a negative electric potential, as shown by the brokenline in FIG. 46(b), the transmittances on the end electrodes (positiveelectrodes) 32 and 34 become lower than that on the middle electrode(negative electrode) 33. Therefore, when some of the plurality ofelectrodes 32, 33 and 34 is/are made transparent, frames where thetransparent electrode(s) have a negative electric potential becomebrighter than frames where the transparent electrode(s) have a positiveelectric potential, causing flicker.

[0017] Taking these phenomena, which are key causes of flicker, intoconsideration, transmittances of individual pixels in prior art displaydevices are not even but exhibit a certain distribution, i.e., thetransmittance distribution varies between when a pixel electrode has apositive electric potential relative to the opposing electrode (positiveframe) and when the pixel electrode has a negative electric potentialrelative to the opposing electrode (negative frame). Therefore, forexample, when the pixel electrode is made of a transparent material andthe opposing electrode is made of an opaque material, the transmittanceof the pixel electrode in either the positive or negative frame becomeshigher than that of the other frame. On the other hand, the opposingelectrode does not transmit light and therefore the transmittance of theopposing electrode does not change between a positive frame and anegative frame. As a result, the transmittance variance between framesof the pixel electrode is observed as a variance in the brightness ofthe whole pixel.

[0018] Such a flicker phenomenon is not limited to IPS style liquidcrystal display devices but occurs when display devices comprising twoelectrodes having different light transmittances are driven by thealternating current drive method.

[0019] To achieve the above object, the display device of the inventioncomprises an array substrate, an opposing substrate facing the arraysubstrate and an electro-optic substance held between the arraysubstrate and the opposing substrate. The array substrate is providedwith a plurality of gate wirings and a plurality of source wiringsintersecting each other, a pixel electrode disposed in each regiondefined by two adjacent gate wirings and two adjacent source wirings, aswitching element for switching a voltage applied to the pixel electrodefrom the source wiring based on a signal voltage supplied from the gatewiring, a common wiring formed between the two adjacent gate wirings andan opposing electrode being electrically connected to the common wiringand generating an electric field for driving the electro-optic substancebetween the opposing electrode and the pixel electrode whereto a voltageis applied. The pixel electrode comprises a first pixel electrode and asecond pixel electrode, and the opposing electrode comprises a firstopposing electrode and a second opposing electrode. A first region isformed in which an electric field is generated between the first pixelelectrode and the first opposing electrode whose light transmittance islower than that of the first pixel electrode. A second region is alsoformed in which an electric field is generated between the second pixelelectrode and the second opposing electrode whose light transmittance ishigher than that of the second pixel electrode. According to thisdisplay device, flicker can be reduced because the flicker polaritiescaused by the variance in transmittance between the pixel electrode andthe opposing electrode can be cancelled between the first region and thesecond.

[0020] In the display device, it is preferable that the first region andthe second region be adjacent to each other.

[0021] It is preferable that a voltage is applied to the first pixelelectrode and the second pixel electrode from the same source wiringbased on the signal voltage supplied from the same gate wiring. Thismakes the polarities of a voltage applied to the first pixel electrodeand second pixel electrode the same and reliably cancel flickerpolarity.

[0022] Preferably, the first region and the second region be disposed inthe same dot. This makes it possible to locate the interface of thefirst region and the second region on the common electrode. It is alsopossible to connect the first pixel electrode to the second pixelelectrode and the first opposing electrode to the second opposingelectrode respectively through contact holes formed in the insulatinglayers held in between. Thereby, formation of contact hole in apertureof the display region for connecting different electrode materials(material transformation) becomes unnecessary, enhancing a high apertureratio. It is also possible to arrange the source wiring between thefirst region and the second region. A preferable arrangement is suchthat the switching elements each correspond to the first pixel electrodeand second pixel electrode, respectively. This arrangement reduces adefective ratio of the dot. Furthermore, when a plurality of the firstregions and a plurality of the second regions are formed, it ispreferable that groups of two consecutively identical regions bealternately arranged along the gate wiring and the interface of the thatgroups of two adjacent first regions and the second regions be locatedon the pixel electrode or the opposing electrode. This allows any twoadjacent regions to share the pixel electrode or the opposing electrode,enhancing the aperture ratio.

[0023] When a plurality of the first regions and a plurality of thesecond regions are formed, it is preferable that the first regions andthe second regions are arranged in a manner such that the flickerpolarity cyclically changes along both the gate wiring and the sourcewiring based on the prescribed voltage polarity applied to the firstpixel electrode and the second pixel electrode. This reduces flicker andachieves a uniform display without suffering from vertical or horizontalstrips while in operation. In this case, it is preferable that theflicker polarities be inverted at every dot along both the gate wiringand the source wiring. When a checkerboard pattern or the like isdisplayed, it is preferable the flicker polarities be inverted at everyplurality of dots along both the gate wiring and the source wiring.

[0024] It is also possible to arrange the first region and the secondregion in such a manner that each region corresponds to a dot or a pixelcomprising three dots of red, green and blue. In both arrangements,flicker reduction can be achieved in a smaller region.

[0025] When storage capacitor electrodes electrically connected to thefirst pixel electrode and the second pixel electrode are formed and eachof them is arranged in the first region and the second region, the twostorage capacitor electrodes are disposed on the common electrode or thegate wiring with insulating layers in between to form storage capacitorregions. In this case, it is preferable that the capacities of the twostorage capacitor regions be made substantially the same. This can beachieved by forming the two storage capacitor electrodes out of the samematerial and making their surface areas substantially the same.

[0026] The first pixel electrode and the second opposing electrode canbe made of transparent materials and the first opposing electrode andthe second pixel electrode can be made of an opaque material.

[0027] It is preferable that the area of the pixel electrode in theaperture of the first region and the area of the opposing electrode inthe aperture of the second region be made substantially the same,reliably canceling flicker polarities and enhancing the flickerreduction effect. In this case, it is desirable that the transmittancesof the first pixel electrode and the second opposing electrode beapproximately the same. Such an arrangement readily be achieved bycovering some portion of the first opposing electrode or the secondpixel electrode with an opaque layer formed on the opposing substratefor blocking some portion of the array substrate from light.

[0028] It is preferable that a driving voltage having the same polarityis applied to the first region and the second region.

[0029] It is also preferable that first region and the second regionhave substantially the same absolute value of bright difference betweenthe case where the pixel electrode has a positive electric potentialrelative to the opposing electrode and the case where the pixelelectrode has a negative electric potential relative to the opposingelectrode.

[0030] An object of the invention is also achieved by a display devicecomprises an array substrate, an opposing substrate facing the arraysubstrate and an electro-optic substance held between the arraysubstrate and the opposing substrate. The array substrate is providedwith a plurality of gate wirings and a plurality of source wiringsintersecting each other, a pixel electrode disposed in each regiondefined by two adjacent gate wirings and two adjacent source wirings, aswitching element for switching a voltage applied to the pixel electrodefrom the source wiring based on a signal voltage supplied from the gatewiring, a common wiring formed between the two adjacent gate wirings, anopposing electrode being electrically connected to the common wiring andgenerating an electric field for driving the electro-optic substancebetween the opposing electrode and the pixel electrode whereto a voltageis applied and an intermediate electrode disposed between the pixelelectrode and the opposing electrode. The intermediate electrode has atransmittance either higher or lower than both the pixel electrode andthe opposing electrode.

[0031] In this display device, it is preferable that the pixel electrodeand the opposing electrode be formed out of the same material, and theintervals between the pixel electrode and the intermediate electrode andbetween the intermediate electrode and the opposing electrode besubstantially the same.

[0032] It is preferable that the intermediate electrode be resistivelyconnected to the pixel electrode and the opposing electrode or conductcapacity coupling can be performed.

[0033] It is also preferable that the electric potential of theintermediate electrode becomes the average value of the electricpotential of the pixel electrode whereto a voltage is applied and theelectric potential of the opposing electrode which functions as astandard electric potential.

[0034] In the display device described above, it is preferable that theelectro-optic substance be liquid crystal and the voltage applied to thepixel electrode be an alternating voltage.

[0035] An object of the invention can be achieved by applying a drivemethod for use in a display device comprising an array substrate, anopposing substrate facing the array substrate and an electro-opticsubstance held between the array substrate and the opposing substrate.The array substrate is provided with a plurality of gate wirings and aplurality of source wirings intersecting each other, a pixel electrodedisposed in each region defined by two adjacent gate wirings and twoadjacent source wirings, a switching element for switching a voltageapplied to the pixel electrode from the source wiring based on a signalvoltage supplied from the gate wiring, a common wiring formed betweenthe two adjacent gate wirings and an opposing electrode beingelectrically connected to the common wiring and generating an electricfield for driving the electro-optic substance between the opposingelectrode and the pixel electrode whereto a voltage is applied. Thepixel electrode and the opposing electrode are made of the materialshaving different transmittances. In this drive method, the voltageapplied to the pixel electrode is inverted every predetermined adjacentregions.

[0036] In this drive method, the flicker polarities can be canceledbetween the two adjacent regions, reducing flicker.

[0037] It is preferable that the predetermined regions be adjacent toeach other in two directions along the gate wiring and the sourcewiring.

[0038] It is also preferable that each predetermined region correspondto a dot or two dots adjacent in a direction either along the gatewiring or the source wiring.

[0039] The predetermined region can correspond to a pixel composed ofthree dots of red, green and blue or two adjacent pixels each composedof three dots of red, green and blue, wherein the any two adjacentpixels are adjacent to each other in a direction either along the gatewiring or the source wiring.

[0040] An object of the invention can be achieved by applying a drivemethod for use in a display device comprising an array substrate, anopposing substrate facing the array substrate and an electro-opticsubstance held between the array substrate and the opposing substrate.The array substrate is provided with a plurality of gate wirings and aplurality of source wirings intersecting each other, a pixel electrodedisposed in each region defined by two adjacent gate wirings and twoadjacent source wirings, a switching element for switching a voltageapplied to the pixel electrode from the source wiring based on a signalvoltage supplied from the gate wiring, a common wiring formed betweenthe two adjacent gate wirings and an opposing electrode beingelectrically connected to the common wiring and generating an electricfield for driving the electro-optic substance between the opposingelectrode and the pixel electrode whereto a voltage is applied. Thepixel electrode and the opposing electrode are made of the materialshaving different transmittances. The voltage applied to the pixelelectrode is inverted by increasing or decreasing the volume ofprescribed brightness compensation voltage.

[0041] This method for driving a display device makes the brightnessdifferences approximately the same when the polarity of a voltageapplied to the pixel electrode is inverted, reducing flicker.

[0042] When both the pixel electrode and the opposing electrode areformed out of transparent electric conductors, this method for driving adisplay device can be applied to the case where the total area of thepixel electrode and the total area of the opposing electrode occupyingthe transparent portions in the regions are different from each other.

[0043] An object of the invention can be achieved by applying a drivemethod for use in a display device comprising an array substrate, anopposing substrate facing the array substrate and an electro-opticsubstance held between the array substrate and the opposing substrate.The array substrate is provided with a plurality of gate wirings and aplurality of source wirings intersecting each other, a pixel electrodedisposed in each region defined by two adjacent gate wirings and twoadjacent source wirings, a switching element for switching a voltageapplied to the pixel electrode from the source wiring based on a signalvoltage supplied from the gate wiring, a common wiring formed betweenthe two adjacent gate wirings and an opposing electrode beingelectrically connected to the common wiring and generating an electricfield for driving the electro-optic substance between the opposingelectrode and the pixel electrode whereto a voltage is applied. Thepixel electrode comprises a first pixel electrode and a second pixelelectrode, and the opposing electrode comprises a first opposingelectrode and a second opposing electrode. A plurality of first regionsgenerating an electric field between the first pixel electrode and thefirst opposing electrode whose light transmittance is lower than that ofthe first pixel electrode are formed; and a plurality of second regionsgenerating an electric field between the second pixel electrode and thesecond opposing electrode whose light transmittance is lower than thatof the second pixel electrode are formed. A voltage applied to the firstpixel electrode and the second pixel electrode is inverted based on thearrangement cycles of the first region and the second region so as toflicker polarities periodically change along both the gate wiring andthe source wiring.

[0044] This drive method can cancel flicker and prevent vertical orhorizontal strips from appearing on a display during operation.

[0045] It is preferable that the flicker polarities are inverted atevery dot or every plurality of dots along both or either of the gatewiring and the source wiring.

[0046] In the drive method, it is preferable that the driving frequencyof the voltage applied to the pixel electrode be 60Hz or higher forcancel apparent flicker.

BRIEF DESCRIPTION OF THE DRAWINGS

[0047]FIG. 1 is a plan view showing a structure of one dot serving as aminimal display unit of an array substrate in a display device accordingto Embodiment 1 of the present invention.

[0048] FIGS. 2(a), 2(b) and 2(c) are sectional views of FIG. 1.

[0049]FIGS. 3 and 4 illustrate operations of the structure shown in FIG.1.

[0050]FIG. 5 is a plan view showing a structure of one dot serving as aminimal display unit of an array substrate in a display device accordingto Embodiment 2 of the invention.

[0051] FIGS. 6(a), 6(b), 6(c) and 6(d) are sectional views of FIG. 5.

[0052]FIG. 7 is a plan view showing a structure of one dot serving as aminimal display unit of an array substrate in a display device accordingto Embodiment 3 of the invention.

[0053]FIG. 8 is a plan view showing a structure of one dot serving as aminimal display unit of an array substrate in a display device accordingto Embodiment 4 of the invention.

[0054] FIGS. 9(a) and 9(b) are sectional views of FIG. 8.

[0055]FIG. 10 is a plan view showing a structure of one dot serving as aminimal display unit of an array substrate in a display device accordingto Embodiment 5 of the invention.

[0056] FIGS. 11(a) and 11(b) are sectional views of FIG. 10.

[0057] FIGS. 12(a) and 12(b) schematically illustrate arrays of dots.

[0058] FIGS. 13(a), 13(b), 13(c), 13(d), 13(e) and 13(f) schematicallyillustrate several methods for inverting a driving voltage.

[0059]FIG. 14 is a plan view showing a structure of one dot serving as aminimal display unit of an array substrate in a display device accordingto Embodiment 6 of the invention.

[0060] FIGS. 15(a), 15(b) and 15(c) are sectional views of FIG. 14.

[0061]FIG. 16 is a plan view showing a structure of one dot serving as aminimal display unit of an array substrate in a display device accordingto Embodiment 7 of the invention.

[0062] FIGS. 17(a), 17(b), 17(c) and 17(d) are sectional views of FIG.16.

[0063]FIG. 18 shows the equivalent circuit of the structure shown inFIG. 16.

[0064]FIG. 19 is a plan view showing a structure of one dot serving as aminimal display unit of an array substrate in a display device accordingto Embodiment 8 of the invention.

[0065] FIGS. 20(a), 20(b), 20(c), and 20(d) are plan views of FIG. 19.

[0066]FIG. 21 shows the equivalent circuit of the structure shown inFIG. 19.

[0067]FIG. 22 is a plan view showing a modification of the structureshown in FIG. 19.

[0068]FIG. 23 is a plan view showing the structures of two adjacent dotson an array substrate in a display device according to Embodiment 9 ofthe invention.

[0069] FIGS. 24(a), 24(b) and 24(c) are sectional views of FIG. 23.

[0070]FIG. 25 is a plan view showing the structures of two adjacent dotson an array substrate in a display device according to Embodiment 10 ofthe invention.

[0071] FIGS. 26(a), 26(b) and 26(c) are sectional views of FIG. 25.

[0072]FIG. 27 schematically shows an array of dots in a pixel of a colordisplay device.

[0073]FIG. 28 shows schematic structure of a display device according toEmbodiment 11 of the invention.

[0074]FIG. 29 schematically shows arrases of dots in two adjacent pixelsof a display device according to Embodiment 12 of the invention.

[0075]FIG. 30 schematically shows arrays of dots in two adjacent pixelsof a display device according to Embodiment 13 of the invention.

[0076] FIGS. 31(a), 31(b), 31(c), 31(d), 31(e) and 31(f) schematicallyshow the polarities of drive waveforms on odd frames, dot structure andflicker polarities of a display device according to Embodiment 14 of theinvention.

[0077] FIGS. 32(a), 32(b), 32(c) and 32(d) schematically show thepolarities of drive waveforms on odd frames, dot structure and flickerpolarities of a display device according to Embodiment 15 of theinvention.

[0078] FIGS. 33(a) and 33(b) are sectional view and plan view of adisplay device according to Embodiment 16 of the invention.

[0079]FIG. 34 is an expanded sectional view showing the structure arounda switching element of a display device according to Embodiment 16 ofthe invention.

[0080]FIG. 35(a). is a plan view showing a 4×4 dot section of pixels andFIGS. 35(b) and 35(c) are schematic diagrams showing writing polaritiesto the pixels of a display device according to Embodiment 16 of theinvention.

[0081] FIGS. 36(a) and 36(b) show light transmittance properties of apixel portion in a display device according to Embodiment 16 of theinvention.

[0082] FIGS. 37(a) and 37(b) are sectional view and plan view of adisplay device according to Embodiment 17 of the invention.

[0083]FIG. 38 is an expanded sectional view showing the structure arounda switching element of a display device according to Embodiment 17 ofthe invention.

[0084]FIG. 39(a) is a plan view showing a 4×4 dot section of pixels of adisplay device according to Embodiment 17 of the invention, and FIG.39(b) is a schematic diagram showing the waveform applied to each of thepixels.

[0085] FIGS. 40(a) and 40(b) show light transmittance properties of apixel portion in a display device according to Embodiment 17 of theinvention.

[0086]FIG. 41 is a plan view showing a display device according toEmbodiment 18 of the invention.

[0087]FIG. 42 is a plan view showing another display device according toEmbodiment 18 of the invention.

[0088] FIGS. 43(a) and 43(b) show operation of a display deviceaccording to another embodiment of the invention.

[0089] FIGS. 44(a), 44(b), 44(c) and 44(d) illustrate a first factorcausing flicker.

[0090] FIGS. 45(a) and 45(b), and FIGS. 46(a) and (b) illustrate asecond factor causing flicker.

[0091]FIG. 47 is a plan view showing a prior art display device.

BEST MODE FOR CARRYING OUT THE INVENTION

[0092] Embodiments of the present invention will be described below withreference to the drawings.

[0093] (Embodiment 1)

[0094]FIG. 1 is a plan view showing a structure of one dot serving as aminimal display unit of an array substrate in a display device accordingto Embodiment 1 of the invention. FIGS. 2(a), 2(b) and 2(c) aresectional views of FIG. 1 taken along the lines A-A′, B-B′ and C-C′,respectively. In FIG. 1, gate wirings 4 feeding scanning signals andsource wirings 7 feeding image signals are arranged so as to intersectat approximately right angles. Nearby each intersection of the gatewiring 4 and the source wiring 7, a thin-film transistor (TFT) 5 isformed as a switching element. The TFT 5 formed on the gate wiring 4with an insulating layer in between comprises a semiconductor layer 8made of amorphous silicon. On the two sides of the semiconductor layer8, a projecting part of the source wiring 7 and a drain electrode 6 arearranged facing each other.

[0095] To the source wiring 7, a pixel electrode 1 is connected via thedrain electrode 6 of the TFT 5. An opposing electrode 2 functioning as astandard potential is arranged so as to face the pixel electrode 1. Theopposing electrode 2 is disposed between the two gate wirings 4, 4 in aparallel manner, and electrically connected to a common wiring 3 whichsupplies a prescribed electric potential (opposing voltage) to theopposing electrode 2.

[0096] The pixel electrode 1 comprises a first pixel electrode 1 a madeof a transparent electric conductor disposed in the upper half of thedot and a second pixel electrode 1 b made of a metal material disposedin the lower half of the dot. The opposing electrode 2 comprises a firstopposing electrode 2 a made of a metal material which is disposed in theupper half of the dot so as to face the first pixel electrode 1 a and asecond opposing electrode 2 b made of a transparent electric conductordisposed in the lower half of the dot so as to face the second pixelelectrode 1 b.

[0097] On the gate wiring 4, a storage capacitor region 10 connected tothe first pixel electrode 1 a is formed with an insulating layer inbetween.

[0098] As shown in FIGS. 1, 2(a), 2(b) and 2(c), on an array substrate9, the gate wiring 4, the first opposing electrode 2 a and a commonwiring 3 a are formed out of a first metal layer (ex. a three-layeredstructure comprising titanium, aluminum and titanium). There upon, withan insulating layer 11 a in between, the source wiring 7, the drainelectrode 6 and the second pixel electrode 1 b are formed out of asecond metal layer (ex. a three-layered structure comprising titanium,aluminum and titanium). There upon, with an insulating layer 11 b inbetween, the first pixel electrode 1 a and the second opposing electrode2 b are formed out of a transparent electric conductor layer (ex.Indium-Tin-Oxide (ITO)). The semiconductor layer 8 is formed between thefirst metal layer and the second metal layer and subjected topatterning. Both of the metal layers can be a uniform layer instead of amultilayer. For example, they can be formed of chromium, aluminum,tantalum or the like. It is also possible to use an alloy of molybdenumand tungsten, an alloy of molybdenum and tantalum or like alloys.Particularly, using silver alloys (ex. an alloy of silver, palladium andcopper) is advantageous in that it lowers the wiring resistance andsimplifies the manufacturing process. Tin oxide and like oxides, organicconductive films as well as ITO can be used for forming the transparentelectric conductor layer.

[0099] The first pixel electrode 1 a and the second pixel electrode 1 bare connected to each other through a contact hole 13 formed in theinsulating layer 11 b. The first opposing electrode 2 a is connected tothe common wiring 3 formed on the same layer, and the second opposingelectrode 2 b is connected to a common wiring through a contact hole 14formed in the insulating layers 11 a, 11 b. The number of contact holesand layer transformations (connections between different layers) areadjusted based on the shape and the number of electrodes.

[0100] Between the array substrate 9 and the opposing substrate (notshown) structured as described above, liquid crystal (not shown) issealed in. Thus, a display device can be obtained.

[0101] The operation of the display device is described below. When anon-status voltage is applied to the gate wiring 4, a channel is formedon the semiconductor layer 8 and the gap between the source wiring 7 andthe drain electrode 6 becomes conductive. Then, the drain electrode 6and the pixel electrode 1 are charged to have the same electricpotential as that of the source wiring 7. Thereby, a difference appearsbetween the voltage fed to the pixel electrode 1 and that of theopposing electrode 2, to which a standard electric potential is applied.This generates electric fields substantially parallel to the substratesbetween the first pixel electrode 1 a and the first opposing electrode 2a and between the second pixel electrode 1 b and the second opposingelectrode 2 b and applied to the liquid crystal held between each of theelectrodes.

[0102] When an off-status voltage is applied to the gate wiring 4,channel formation is not achieved in the semiconductor layer 8, andtherefore there is no electrical continuity between the source wiring 7and the drain electrode 6 and the electric charges charged in the drainelectrode 6 and the pixel electrode 1 are retained. A storage capacitorelectrode 10 forms a storage capacitor region between the gate wiring 4and stabilizes the operation of the display device by compensating foror alleviating the potential difference due to leakage of electriccharge from the pixel electrode 1. Operation observed in one dot isexplained above. In a display device as a whole, a prescribed electricpotential is sent to each of the dots arranged in a matrix whilescanning the gate wirings one by one and applying to the source wiring asignal voltage appropriate to the dot scanned.

[0103] Operation of a display device according to the present embodimentwill be described below in more detail with reference to FIGS. 3 and 4.The structure shown in FIGS. 3 and 4 is the same as that shown in FIG.2, and therefore the reference symbols used in FIG. 2 are omitted inFIGS. 3 and 4 unless needed for explanation.

[0104] The signal voltage of each dot alternates in every frame in amanner such that the electric potential of the pixel electrode 1 assumesa positive or negative value relative to the opposing electrode 2. FIG.3 shows the condition where the gate voltage is at the off-level(Vg(OFF)) after creating a positive electric potential in the pixelelectrode 1 in the first frame. FIG. 4 shows the condition where thegate voltage is at the off-level after recording a negative electricpotential into the pixel electrode in the second frame. The displaydevice, while the first and the second frames are being alternatelyrepeated, is driven by the alternating current drive method. To simplifythe explanation, the electric potential of the opposing electrode 2 ismade a constant ground potential; however, if modulation in accordancewith the polarity of the pixel electric potential is added to theopposing voltage and the gate voltage, the amplitude of the signalvoltage can be reduced.

[0105] As shown in FIG. 3, in the first frame, the first pixel electrode1 a and the second pixel electrode 1 b have a positive electricpotential and the first opposing electrode 2 a and the second opposingelectrode 2 b have a ground potential, generating an electric field asshown by the arrows in the figure. Therefore, in the upper half of thedot, an electric field is generated from the transparent first pixelelectrode 1 a to the opaque first opposing electrode 2 a and thetransparent electrode (the shadowed portion of the figure) has arelatively positive electric potential; however, in the lower half ofthe dot, an electric field is generated from the opaque second pixelelectrode 1 b to the transparent second opposing electrode 2 b and thetransparent electrode (shadowed portion of the figure) has a relativelynegative electric potential.

[0106] On the other hand, as shown in FIG. 4, in the second frame, thefirst pixel electrode 1 a and the second pixel electrode 1 b have anegative electric potential and the first opposing electrode 2 a and thesecond opposing electrode 2 b have a ground potential, generating anelectric field as shown by the arrows in the figure. Therefore, in theupper half of the dot, an electric field is generated from the opaquefirst opposing electrode 2 a to the transparent first pixel electrode 1a and the transparent electrode (shadowed portion of the figure) has arelatively negative electric potential; however, in the lower half ofthe dot, an electric field is generated from the transparent secondopposing electrode 2 b to the opaque second pixel electrode 1 b and thetransparent electrode (shadowed portion of the figure) has a relativelypositive electric potential.

[0107] The light passing through spaces or transparent electrodes(shadowed portion of the figure) in a dot, becomes brighter in portionswhere, among the pixel electrode 1 and the opposing electrode 2, thetransparent electrode has a negative electric potential relative to theopaque electrode compared to portions where the transparent electrodehas a positive electric potential relative to the opaque electrode.Therefore, in the first frame shown in FIG. 3, the lower half of the dotis brighter and, in the second frame shown in FIG. 4, the upper half ofthe dot becomes brighter. As described above, either the upper half orthe lower half of the dot alternately becomes brighter, and thereforethe contrast within a dot is canceled from frame to frame and theflicker phenomenon does not occur.

[0108] In the present embodiment, since the partition line which dividesthe dot into the upper and lower portions exists on the common wiring 3,two regions having opposite flicker polarities (light or dark polarity)can be formed in a single display unit without an additional electrodelayer or switching element. Therefore, the embodiment has the advantagethat flicker can be reduced or eliminated without increased productioncosts caused by a more complicated manufacturing process or loweredaperture ratio due to formation of a switching element.

[0109] In addition, the layer transformation and the materialtransformation (connections between different layers and materials) ofthe first and second pixel electrodes 1 a, 1 b and the first and secondopposing electrodes 2 a, 2 b occur above the common wiring 3, andtherefore there is no need to form contact holes 13, 14 in the apertureportion of the display region to make the connections, improving theaperture ratio. Furthermore, in the structure where the common wiring 3is disposed near the center of the display unit as in the presentembodiment, if the connections between the electrode materials are madeabove the common wiring 3, the areas of the two regions having differentflicker polarities can be made almost equal, and a great reduction offlicker can be achieved by a simple structure. Generally speaking, theabove-mentioned improvement in the aperture ratio can be achieved if theconnections between the electrode materials are made above the commonwiring or the gate wiring.

[0110] (Embodiment 2)

[0111]FIG. 5 is a plan view showing the structure of one dot serving asa minimal display unit of an array substrate in a display deviceaccording to Embodiment 2 of the invention and FIGS. 6(a), 6(b), 6(c)and 6(d) are sectional views of FIG. 5 taken along the lines D-D′, E-E′,F-F′ and G-G′. In FIG. 5 and FIGS. 6(a), 6(b), 6(c) and 6(d), thoseelements which are identical to the elements of Embodiment 1 shown inFIGS. 1, 2(a), 2(b), and 2(c) are identified with the same numericalsymbols, and repetitious explanation will be omitted.

[0112] A display device of the present embodiment is different from thatof Embodiment 1 in that a storage capacitor electrode 10 is formed onthe common wiring 3 instead of on the gate wiring 4 and a storagecapacitor region is formed between the common wiring 3 and the storagecapacitor electrode 10. This arrangement makes it possible to eliminatean additional capacitor above the gate wiring 4 and achieve an uniformdisplay with a reduced distortion of the scanning voltage even on a widescreen. The principle used to eliminate flicker is the same as that usedin Embodiment 1.

[0113] In Embodiment 1, the storage capacitor electrode 10 is formed outof the second metal layer in the same layer as the source wiring 7, thedrain electrode 6 and the second pixel electrode 1 b and is connected tothe second pixel electrode 1 b. Via the contact hole 13, the storagecapacitor electrode 10 is also connected to the first pixel electrode 1a which is formed out of a transparent electric conductor layer with aninsulating layer 11 b in between.

[0114] Therefore, as Embodiment 1, the structure of the presentembodiment has the following advantages. By dividing the region (dot)constituting display unit into upper and lower portions and connectionsbetween the different materials (material transformation) of the pixelelectrode 1 and the opposing electrode 2 on the common wiring 3corresponding to the partition line, it is possible to reduce oreliminate flicker without suffering from increased production costscaused by a more complicated manufacturing process or a lowered apertureratio attributable to the formation of a switching element. Furthermore,since connections between the electrode materials are made above thewiring, formation of a contact hole in the aperture of the displayregion for making connections between different materials becomesunnecessary, and this enhances the aperture ratio.

[0115] In the following embodiments, the storage capacitor electrode isformed on the common wiring 3 as in the present embodiment; however, itcan be formed on the gate wiring 4 as in Embodiment 1.

[0116] (Embodiment 3)

[0117]FIG. 7 is a plan view showing the structure of one dot serving asa minimal display unit of an array substrate in a display deviceaccording to Embodiment 3 of the invention. In FIG. 7, those elementswhich are identical to the elements of Embodiment 1 shown in FIG. 1 areidentified with the same numerical symbols, and repetitious explanationwill be omitted.

[0118] In the display device of the present embodiment, the region 81corresponding to the black matrix formed as an opaque layer on theopposing substrate (not shown) facing the array substrate shown in FIG.1 is indicated by the region outlined with broken lines and filled byoblique lines. In other words, the region 81 is an area where passinglight is blocked, and an aperture is formed in the center of the dot.

[0119] The outline of the region 81 runs along the middle of the firstopposing electrode 2 a and the second opposing electrode 2 b in thelongitudinal direction and makes the areas of the transparent electrodedisposed in the apertures in the upper and lower halves of a dot (i.e.the first pixel electrode 1 a and the second opposing electrode 2 b)equal. As a result, it is possible to reliably cancel the flickerpolarities in a dot. This structure is particularly useful when theactual areas of the transparent electrode differ in the upper and lowerhalves of a dot. In the present embodiment, the areas of the transparentelectrode in the apertures in the upper and lower halves of a dot aremade equal using a black matrix; however, it is also possible to makethe areas of the transparent electrode equal by varying the width of theelectrode and adjusting the length of the electrode. The black matrixcan be formed on the array substrate side. Furthermore, it is alsopossible to use a metal layer instead of the black matrix and make itfunction as an opaque layer by overlaying it on a part of thetransparent electrode layer. By forming an opaque layer such as a blackmatrix or the like on the array substrate side, the effect of anymisalignment of the two substrates is eliminated and the accuracy of theposition of the opaque layer with respect to the electrode is enhanced.This enhances the ability to eliminate flicker. More preferably, flickercan be reliably prevented by utilizing the results of experiments orsimulations and adjusting the width of the opaque layer and electrodeand the length of the electrode in a manner such that the effectiveareas of the transparent electrode affecting the transmittance in theupper and lower halves of a dot becomes equal. This arrangement can beemployed not only in a display device of Embodiment 1 but also indisplay devices of other embodiments.

[0120] (Embodiment 4)

[0121]FIG. 8 is a plan view showing the structure of one dot serving asa minimal display unit of an array substrate in a display deviceaccording to Embodiment 4 of the invention. FIGS. 9(a) and 9(b) aresectional views of FIG. 8 taken along the lines H-H′ and I-I′. In FIGS.8, 9(a) and 9(b), those elements which are identical to the elements ofEmbodiment 1 shown in FIGS. 1, 2(a), 2(b), and 2(c) are identified withthe same numerical symbols, and repetitious explanation will be omitted.

[0122] A display device according to the present embodiment is designedso that the inside of a dot is divided into right and left halves andflicker is canceled between the two (left and right) regions.

[0123] The right region comprises a first pixel electrode 1 a made of atransparent electric conductor and a first opposing electrode 2 a madeof a metal material. The left region comprises a second pixel electrode1 b made of a metal material and a second opposing electrode 2 b made ofa transparent electric conductor. In the center of the dot, with theboundary line of the left and right regions in between, a first centralopposing electrode 2 c made of a metal material is formed on the rightside and a second central opposing electrode 2 d made of a transparentelectric conductor is formed on the left side. A common wiring 3 isdisposed above the center of the dot.

[0124] As shown in FIGS. 8, 9(a) and 9(b), on an array substrate 9, agate wiring 4, the first opposing electrode 2 a, the common wiring 3 andthe first central opposing electrode 2 c are formed out of a first metallayer. There upon, with an insulating layer 11 a in between, a sourcewiring 7, a drain electrode 6, the second pixel electrode 1 b and astorage capacitor electrode 10 are formed out of a second metal layer.Above the second metal layer, with an insulating layer 11 b in between,the first pixel electrode 1 a, the second opposing electrode 2 b and thesecond central opposing electrode 2 d are formed out of a transparentelectric conductor layer. The first pixel electrode 1 a is connected tothe storage capacitor electrode 10 through a contact hole 13, and thesecond opposing electrode 2 b and the second central opposing electrode2 d are connected to the common wiring 3 through a contact hole 14.

[0125] The display device having the above structure is advantageous inthat it prevents flicker and readily obtains high definition imagesowing to a reduced number of contact holes. Furthermore, it can enhancethe manufacturing yield since the ratio of defects caused by poorcontact between the constituent elements is lowered. The common wiring 3can also be disposed below the center of the dot.

[0126] (Embodiment 5)

[0127]FIG. 10 is a plan view showing the structure of one dot serving asa minimal display unit of an array substrate in a display deviceaccording to Embodiment 5 of the invention. FIGS. 11(a) and 11(b) aresectional views of FIG. 10 taken along the lines J-J′ and K-K′. In FIGS.10, 11(a) and 11(b), those elements which are identical to the elementsof Embodiment 1 shown in FIGS. 1, 2(a), 2(b), and 2(c) are identifiedwith the same numerical symbols, and repetitious explanation will beomitted.

[0128] In FIG. 10, the region 41, whose outline is shown by the brokenline, indicates a region of one dot. In the present embodiment, the dotis divided into two subdots SD1 and SD2 having opposite flickerpolarities (light or dark polarity) and the flicker polarities arecanceled within the dot.

[0129] The two subdots SD1 and SD2 are formed by dividing the dot intoleft and right portions with the center at a source wiring 7. Theportions receive signals from the same gate wiring 4 and source wiring7. The right subdot SD1 comprises a first pixel electrode 1 a made of atransparent electric conductor and a first opposing electrode 2 a madeof a metal material. In contrast to SD1, the left subdot SD2 comprises asecond pixel electrode 1 b made of a metal material and a secondopposing electrode 2 b made of a transparent electric conductor. Thefirst pixel electrode 1 a and the second pixel electrode 1 b areconnected to the same source wiring 7 through TFTs 42, 43, respectively.Storage capacitor electrodes 10 b, 10 c are formed on a common wiring 3and connected to the first pixel electrode 1 a and the second pixelelectrode 1 b, respectively.

[0130] As shown in FIGS. 10, 11(a) and 11(b), on an array substrate 9,the gate wiring 4, the first opposing electrode 2 a and the commonwiring 3 are formed out of a first metal layer. There upon, with aninsulating layer 11 a in between, the source wiring 7, drain electrodes6 a, 6 b, the second pixel electrode 1 b and the storage capacitorelectrodes 10 b, 10 c are formed out of a second metal layer. Thereupon, with an insulating layer 11 b in between, the first pixelelectrode 1 a and the second opposing electrode 2 b are formed out of atransparent electric conductor layer. The first pixel electrode 1 a isconnected to the storage capacitor electrode 10 b through the contacthole 13, and the second opposing electrode 2 b is connected to thecommon wiring 3 through the contact hole 14.

[0131] This structure achieves a display which is free from flicker,since the difference in brightness attributable to the flexoelectriceffect or a peripheral electric potential is offset between the left andright subdots.

[0132] In the display device of the present embodiment, each dot isdivided into two subdots SD1 and SD2, and the TFTs 42, 43 are providedin the subdots SD1 and SD2, respectively. Therefore, even when a defectarises in one of the TFTs 42, 43, the subdot having the other TFToperates normally. Therefore, the display device has the advantage thatthere is a low possibility of having a non-lighting dot caused by anentire dot being defective.

[0133] Furthermore, the two subdots SD1 and SD2 are arranged so as tohold the source wiring 7 in between. Since both subdots SD1 and SD2 usethe same source wiring 7, there is no need to increase the number ofsource wirings 7.

[0134] As shown in FIG. 10, the electrodes 1 a and 2 b extend upward anddownward from the contact holes 13, 14. Therefore, the number of contactholes can be reduced in the present embodiment compared to the structurein Embodiments 1 and 2 in which the electrodes extend in only onedirection from the contact holes. This makes it possible to readilyprovide high definition images and enhance the manufacturing yield sincethe probability of a defect caused by poor contact between theconstituent elements is lowered.

[0135] In order to further enhance the flicker reducing effect, bringingthe flicker polarities of the two dots into balance is desirable. Forthat purpose, it is desirable that the capacities of the two storagecapacitor electrodes 10 b, 10 c be made equal and it is advantageousthat the two storage capacitor electrodes 10 b, 10 c be designed to beformed of the same material, thereby making the areas of the two storagecapacitor electrodes equal. For that purpose, in the right subdot SD1 ofthe present embodiment, the transparent first pixel electrode 1 a makesa connection between layers and the storage capacitor electrode 10 b ismade out of a metal layer. As a result, the design period of the TFTarray is shortened without adversely affecting the design, enhancing themanufacturing yield by using a design having a high tolerance for theerrors introduced by the manufacturing process.

[0136] Next, examples of the repeated patterns of dots in the entirearray substrate and desirable combinations with driving methods will beexplained. FIGS. 12(a) and 12(b) show repeated patterns of the subdotsSD1 and SD2 shown in FIG. 10, wherein the left subdot SD2 (the pixelelectrode is made out of a metal layer) is defined as P and the rightsubdot SD1 (the pixel electrode is made out of a transparent electrodelayer) is defined as Q. As shown in FIG. 10, between each pair of dots,there is either a first opposing electrode 2 a or a second opposingelectrode 2 b. With respect to the pattern design, the structure inwhich the left and right dots share the first opposing electrode 2 a orthe second opposing electrode 2 b is preferable to enhance the apertureratio. Therefore, in the dot array arranged along the gate wiring 4, onthe right side of a dot having the two subdots arranged in the order ofPQ, it is preferable to place a dot having the two subdots arranged inthe order of QP. In other words, for any two horizontally adjacent dots,it is preferable that the arrangement of the subdots thereof bereversed.

[0137] On the other hand, regarding vertically adjacent dots, it ispreferable that the arrangement cycle of the subdots differ from theinversion cycle of the driving voltages. If the two cycles arecoincident with each other, the effect of inversion is offset andvertical lines may arise because dots having the same flicker polarityare arranged along the source wiring 7.

[0138] Desirable subdot patterns are explained below with reference toconcrete examples. Regarding the subdot arrangement of verticallyadjacent dots, the following two patterns are better suited forpractical use in view of the layout design. In the first pattern, asshown in FIG. 12(a), the arrangement of the right and left subdots isreversed between any two vertically adjacent dots, and in the other, asshown in FIG. 12(b), the arrangement of the right and left subdots iskept the same without reversing.

[0139] FIGS. 13(a) to 13(f) illustrate conditions in which thepolarities of the voltage applied to each dot are inverted between thetwo frames, showing several polarity driving voltage inversion methods.Among the figures, FIG. 13(a) shows the frame-inversion drive method andFIG. 13(b) shows the column-inversion drive method. In both methods, avoltage is applied in such a manner that dots aligned in the verticaldirection have the same polarity. It is desirable that these drivingmethods be used with the subdot arrangement pattern shown in FIG. 12(a).This is because, in vertically adjacent rows, subdot arrays are invertedand the polarity of the voltage applied to the pixel electrodes is thesame, making flicker more indistinctive as subdots having the sameflicker polarities are not continuously aligned in the verticaldirection.

[0140] Among the polarity inversion methods shown in FIGS. 13(a) to13(f), it is preferable that the line-inversion drive method(row-inversion drive method) shown in FIG. 13(c) and the dot-inversiondrive method shown in FIG. 13(d) be used with the subdot arrangementpattern shown in FIG. 12(b). This is because, in vertically adjacentrows, subdot arrays have the same polarity pattern and the polarity ofthe voltage applied to the pixel electrodes is inverted, making flickermore indistinctive as subdots having the same flicker polarities are notcontinuously aligned in the vertical direction.

[0141] In the polarity inversion methods used to drive the liquidcrystal, there are several ways in which inversion is performed every nlines instead of every line as shown in FIGS. 13(c) and 13(d). Thetwo-line inversion drive method shown in FIG. 13(e) (inversion isperformed every two lines) and the two-line-dot inversion drive methodshown in FIG. 13(f) are the examples of the case when n is 2. Wheninversion drive is performed every n lines, a display free from severeproblems in visibility can be achieved if the subdot array is invertedevery n lines and the array cycle differs from the inversion cycle ofthe driving voltage.

[0142] When combined with the subdot arrangement shown in FIG. 12(a),the flicker polarities of vertically adjacent subdots are repeatedlyinverted for n lines and a portion appears every n lines wherevertically adjacent subdots have the same flicker polarities. On theother hand, when combined with the subdot arrangement shown in FIG.12(b), vertically adjacent subdots have the same flicker polarities forn lines and a portion appears every n lines where the flicker polaritiesof vertically adjacent subdots are inverted. Therefore, when n is 2, andeither the subdot arrangement shown in FIG. 12(a) or that of 12(b) isadopted, two lines of subdots having the same flicker polarities arecontinuously arranged in the vertical direction and then inverted,obtaining a desirable display. When n is 3 or greater, combination withthe subdot arrangement shown in FIG. 12(a) results in an increasednumber of inversions of flicker polarity, and is thus desirable.

[0143] (Embodiment 6)

[0144]FIG. 14 is a plan view showing the structure of one dot serving asa minimal display unit of an array substrate in a display deviceaccording to Embodiment 6 of the invention and FIGS. 15(a), 15(b), 15(c)and 15(d) are sectional views of FIG. 14 taken along the lines L-L′,M-M′, N-N′ and O-O′. The present embodiment is a combination ofEmbodiments 2 and 5, and therefore those elements which are identical tothe elements of Embodiments 2 and 5 are identified with the samenumerical symbols, and repetitious explanation will be omitted.

[0145] In a display device of the present embodiment, the dot 51, whoseoutline is shown by the broken line in FIG. 14, is divided into twosubdots SD3 and SD4. The flicker polarities are canceled between theupper and lower halves of the subdots SD3 and SD4.

[0146] The two subdots SD3 and SD4 are formed by dividing the dot intoleft and right portions with the center at a source wiring 7. Theportions receive signals from the same gate wiring 4 and source wiring7. The upper portions of the right subdot SD3 and the left subdot SD4comprise a first pixel electrode 1 a made of a transparent electricconductor and a first opposing electrode 2 a made of a metal material.The lower portions of the right subdot SD3 and the left subdot SD4subdot comprise a second pixel electrode 1 b made of a metal materialand a second opposing electrode 2 b made of a transparent electricconductor. The second pixel electrodes 1 b in the subdots SD3 and SD4are connected to the same source wiring 7 through TFTs 42, 43,respectively. Storage capacitor electrodes 10 are formed on the commonwiring 3 in the subdots SD3 and SD4 and connected to the first pixelelectrode 1 a and the second pixel electrode 1 b, respectively.

[0147] As shown in FIGS. 14, 15(a), 15(b), 15(c) and 15(d) on an arraysubstrate 9, the gate wiring 4, the first opposing electrode 2 a and thecommon wiring 3 are formed out of a first metal layer. There upon, withan insulating layer 11 a in between, the source wiring 7, drainelectrodes 6 a, 6 b, the second pixel electrode 1 b and the storagecapacitor electrode 10 are formed out of a second metal layer. Thereupon, with an insulating layer 11 b in between, the first pixelelectrode 1 a and the second opposing electrode 2 b are formed out of atransparent electric conductor layer. The first pixel electrode 1 a isconnected to the storage capacitor electrode 10 through the contact hole13, and the second opposing electrode 2 b is connected to the commonwiring 3 through the contact hole 14.

[0148] In the display device of the present embodiment, as in Embodiment5, each dot is divided into two subdots SD3 and SD4, and the TFTs 42, 43are provided in the subdots SD3 and SD4, respectively. Therefore, evenwhen a defect arises in one of the TFTs 42, 43, the subdot having theother TFT operates normally. Therefore, the display device has theadvantage that there is a low possibility of having a non-lighting dotcaused by an entire dot being defective.

[0149] Furthermore, as in Embodiment 5, the two subdots SD3 and SD4 arearranged so as to hold the source wiring 7 in between. Since bothsubdots SD3 and SD4 use the same source wiring 7, there is no need toincrease the number of source wirings 7.

[0150] A distinctive advantage of the present embodiment is that it canobtain excellent flicker polarities despite its driving method, sincethe two subdots SD3 and SD4 are symmetrically shaped.

[0151] (Embodiment 7)

[0152]FIG. 16 is a plan view showing the structure of one dot serving asa minimal display unit of an array substrate in a display deviceaccording to Embodiment 7 of the invention and FIGS. 17(a), 17(b) and17(c) are sectional views of FIG. 14 taken along the lines P-P′, Q-Q′and R-R′. In FIGS. 16, 17(a), 17(b), 17(c) and 17(d), those elementswhich are identical to the elements of Embodiment 1 shown in FIGS. 1,2(a), 2(b), and 2(c) are identified with the same numerical symbols, andrepetitious explanation will be omitted.

[0153] According to a display device of the present embodiment, a pixelelectrode 1 and an opposing electrode 2 are formed out of a metal layerand an intermediate electrode 61 made of a transparent conductive layeris formed between the two electrodes. The widths of the spaces betweenthe opposing electrode 2 and the intermediate electrode 61 and betweenthe intermediate electrode 61 and the pixel electrode 1 are madeapproximately equal. The pixel electrode 1, the intermediate electrode61 and the opposing electrode 2 are electrically connected to each otherby a resistor 62 having belt-shaped ends.

[0154] As shown in FIGS. 16, 17(a), 17(b) and 17(c), on an arraysubstrate 9, a gate wiring 4, the opposing electrode 2 and a commonwiring 3 are formed out of a first metal layer. There upon, with aninsulating layer 11 a in between, a source wiring 7, a drain electrode6, the pixel electrode 1 and a storage capacitor electrode 10 are formedout of a second metal layer. There upon, with an insulating layer 11 bin between, the intermediate electrode 61 is formed out of a transparentelectric conductor layer. On the intermediate electrode 61, with aninsulating layer 11 c in between, a resistor 62 is formed out of ametal-oxide layer or a semiconductor layer. High-resistance ITO, tinoxide or the like can be used to obtain a metal-oxide layer. An exampleof a semiconductor layer include an amorphous silicon layer.

[0155] The pixel electrode 1 is connected to the resistor 62 through acontact hole 67 formed in the insulating layers 11 b, 11 c. The opposingelectrode 2 is connected to the resistor 62 through a contact hole 68formed in the insulating layers 11 a, 11 b, 11 c. The intermediateelectrode 61 is connected to the resistor 62 through a contact hole 69formed in the insulating layer 11 c.

[0156]FIG. 18 is an equivalent circuit diagram of the array substratedescribed above. In this figure, the opposing electrode 2 is assumed tohave a ground potential through the common wiring 3 and a signalelectric potential (Va) applied to the pixel electrode 1 is assumed tobe positive. In this case, by making the resistances of each resistor 62approximately the same, the electric potential of the intermediateelectrode 61 becomes the average value (Va/2) of the electric potentialsof the pixel electrode 1 and the opposing electrode 2.

[0157] In FIG. 16, the distances between the opposing electrode 2 andthe intermediate electrode 61 and between the intermediate electrode 61and the pixel electrode 1 are assumed to be substantially the same, andtherefore the strengths of the electric fields generated in spaces S1,S2, S3 and S4 which are formed between the electrodes become the sameand their directions are as shown by the arrows in the figure. In thiscase, in the left intermediate electrode 61, the left half serves as apositive electrode relative to space S1 and the right half serves as anegative electrode relative to space S2. On the other hand, in the rightintermediate electrode 61, the left half serves as a negative electroderelative to space S3 and the right half serves as a positive electroderelative to space S4. Therefore, between the left side and the rightside of the intermediate electrode 61 made of a transparent electricconductor, differences in brightness caused by the flexoelectric effector a peripheral electric potential can be cancelled.

[0158] When a negative signal voltage is applied to the next frame, thedirections of the electric fields and operations of each space servingas a positive or a negative electrode are reversed; however, asexplained above, differences in brightness can be cancelled between theright and the left sides of the intermediate electrode 61. Therefore,the brightness of the positive and the negative frames becomes the samein the dot as a whole, eliminating flicker.

[0159] The intermediate electrode 61 is resistively connected to theelectrodes to which an electric potential is applied (the pixelelectrode 1 and the opposing electrode 2), and therefore its electricpotential is stable without floating. This makes it possible to displaystable images.

[0160] In the present embodiment, the intermediate electrode 61 isresistively connected to the pixel electrode 1 and the opposingelectrode 2; however, it can also be arranged so that an externalelectric potential is applied to the intermediate electrode 61 tostabilize the electric potential of the intermediate electrode 61.

[0161] In the present embodiment, the intermediate electrode 61 is madeof a transparent electric conductor and the pixel electrode 1 and theopposing electrode 2 are formed out of a metal layer; however, by makinga connection between layers by forming a contact hole, etc., it is alsopossible to form the pixel electrode 1 and the opposing electrode 2 of atransparent electric conductor and the intermediate electrode 61 out ofa metal layer. This arrangement increases the number of electrodes madeof a transparent electric conductor, obtaining brighter images.

[0162] It is preferable that the electric potential of the intermediateelectrode 61 be the average of the electric potentials of the pixelelectrode 1 and the opposing electrode 2 as in the present embodiment;however, setting the electric potential of the intermediate electrode 61anywhere between those of the pixel electrode 1 and the electricpotential also achieves a flicker reduction.

[0163] According to the present embodiment, the resistor 62 is formed onthe intermediate electrode 61 with the insulating layer 11 c in between;however, it is not necessary to protect the intermediate electrode 61 bythe insulating layer 11 c, if it is free from damage while the resistor62 is being subjected to patterning. Therefore, as shown in FIG. 17(d),it is also possible to form the portion taken along the line P-P′ inFIG. 16 without having the insulating layer 11 c. This allows areduction of the manufacturing processes and production costs.

[0164] In this case, a concrete example of a way to obtain the resistor62 is as follows. A resin-based resistance-material layer is formed onthe intermediate electrode 61 made of ITO and etched using a photoresisthaving a predetermined pattern. It is also possible to use aphotosensitive material as a resin material and directly conductpatterning by exposure to light. As another example, it is also possibleto apply a resistor to only a prescribed area by mask deposition.

[0165] (Embodiment 8)

[0166]FIG. 19 is a plan view showing the structure of one dot serving asa minimal display unit of an array substrate in a display deviceaccording to Embodiment 8 of the invention and FIGS. 20(a), 20(b) and20(c) are sectional views of FIG. 19 taken along the lines S-S′, T-T′and U-U′. In the present embodiment, instead of connecting the pixelelectrode 1, the intermediate electrode 61 and the opposing electrode 2by a resistive element, capacitive coupling is used. In other respects,the construction thereof is the same as that of Embodiment 5. Therefore,in the present embodiment, those elements which are identical to theelements of Embodiment 5 are identified with the same numerical symbols,and repetitious explanation will be omitted.

[0167] As shown in FIG. 19, according to the present embodiment,extensions 71 projecting into the left and the right sides from the topend of the intermediate electrode 61 are formed instead of forming theresistor 62 shown in FIG. 16. By placing the extension 71 on top of thepixel electrode 1 and the opposing electrode 2, coupling capacityregions 72 a, 72 b are formed.

[0168] As shown in FIGS. 19 and 20(a), the extension 71 extending fromthe intermediate electrode 61 is formed on the insulating layer 11 b. Acoupling capacity region 72 a is formed between the extension 71 and thepixel electrode 1 with an insulating layer 11 a in between. A couplingcapacity region 72 b is formed between the extension 71 and the opposingelectrode 2 with the insulating layers 11 a, 11 b in between.

[0169]FIG. 21 shows an equivalent circuit of the array substratedescribed above. Like in Embodiment 7, it is assumed that the opposingelectrode 2 has a ground potential through the common wiring 3 and thata positive signal electric potential (Va) is applied to the pixelelectrode 1. In this case, by making the capacitances of the couplingcapacity regions 72 a, 72 b approximately equal, the electric potentialof the intermediate electrode 61 becomes the average value (Va/2) of theelectric potentials of the pixel electrode 1 and the opposing electrode2.

[0170] Like in Embodiment 7, In FIG. 19, the distances between theopposing electrode 2 and the intermediate electrode 61 and between theintermediate electrode 61 and the pixel electrode 1 are assumed to besubstantially the same, and therefore the strengths of the electricfields generated in spaces S1, S2, S3 and S4 formed between theelectrodes become the same and their directions are as shown by thearrows in the figure. Therefore, as in Embodiment 7, between the leftside and the right side of the intermediate electrode 61 made of atransparent electric conductor, differences in brightness caused by theflexoelectric effect or a peripheral electric potential can becancelled.

[0171] When a negative signal voltage is applied to the next frame, thedirections of the electric fields and the operation of each spaceserving as a positive or a negative electrode are reversed; however, asexplained above, differences in brightness can be cancelled between theright and the left sides of the intermediate electrode 61. Therefore,the brightness of the positive and the negative frames become the samein the dot as a whole, eliminating flicker.

[0172] A display device according to the present embodiment can reducefraction defectives and production costs compared to that of Embodiment7, since formation of a resistor and a coupling part (contact hole)connecting the resistor to each electrode becomes unnecessary.

[0173] In the present embodiment, as in Embodiment 7, by makingconnections with different layers by forming a contact hole, etc., it isalso possible to form the pixel electrode 1 and the opposing electrode 2of a transparent electric conductor and the intermediate electrode 61out of a metal layer. This arrangement increases the number ofelectrodes made of a transparent electric conductor, obtaining brighterimages.

[0174] It is preferable that the electric potential of the intermediateelectrode 61 be the average of the electric potentials of the pixelelectrode 1 and the opposing electrode 2; however, setting the electricpotential of the intermediate electrode 61 anywhere between those of thepixel electrode 1 and the electric potential also achieves a flickerreduction.

[0175] Taking the difference in the thickness of the insulating layersin the coupling capacity regions 72 a, 72 b into consideration, in orderto make the capacities of the coupling capacity regions 72 a, 72 bequal, it is preferable to adjust the opposing area of the electrodes inthe coupling capacity regions 72 a, 72 b. For example, this can be doneby varying the widths of the pixel electrode 1 and the opposingelectrode 2 in the portions where the coupling capacity regions 72 a, 72b are formed.

[0176] In the present embodiment, two intermediate electrodes 61 areseparately arranged; however, as shown in FIG. 22, it is also possibleto connect the two intermediate electrodes 61 by the extension 71. Thisarrangement reliably makes the electric potentials of the twointermediate electrodes 61 equal. FIG. 20(d) shows the sectional viewtaken along the line S-S′ in FIG. 22. In this figure, the left and rightcoupling capacity regions 72 b, 72 b are in parallel, and therefore itis desirable that the total capacity of the two regions 72 b, 72 b beequal to that of the coupling capacity region 72 a. Specifically, thisis achieved by varying the widths of the pixel electrode 1 and theopposing electrode 2 as described above.

[0177] (Embodiment 9)

[0178]FIG. 23 is a plan view showing the structures of two adjacent dotson an array substrate in a display device according to Embodiment 9 ofthe invention. FIGS. 24(a), 24(b) and 24(c) are sectional views takenalong the lines V-V′, W-W′ and X-X′ of FIG. 23.

[0179] In the display device according to Embodiment 5 shown in FIGS.10, 11(a) and 11(b), flicker polarities are cancelled in a dot bydividing the dot into two subdots and making the flicker polaritiesdifferent in each subdot. On the other hand, in the display deviceaccording to the present embodiment, two adjacent dots D1 and D2 arestructured so that the flicker polarities are cancelled between the dotswhen a signal voltage having the same polarity is applied to the twodots D1 and D2. In FIGS. 23, 24(a), 24(b) and 24(c), those elementswhich are identical to the elements of Embodiment 5 are identified withthe same numerical symbols, and repetitious explanation will be omitted.

[0180] As shown in FIG. 23, the left dot D1 comprises a first pixelelectrode 1 a and a first opposing electrode 2 a. The first pixelelectrode 1 a is made of a transparent electric conductor and the firstopposing electrode 2 a is formed out of a metal layer. The right dot D2comprises a second pixel electrode 1 b and a second opposing electrode 2b. The second pixel electrode 1 b is formed out of a metal layer and thesecond opposing electrode 2 b is made of a transparent electricconductor. The first pixel electrode 1 a and the second pixel electrode1 b are connected to separate source wirings 7 via separate TFTs 5. Thestructure of the TFT 5 of the present embodiment is the same as that ofEmbodiment 1. On a gate wiring 4, storage capacitor electrodes 10 d, 10e are formed and connected to the first pixel electrode 1 a and thesecond pixel electrode 1 b, respectively.

[0181] As shown in FIGS. 23, 24(a), 24(b) and 24(c), on an arraysubstrate 9, the gate wiring 4, the first opposing electrode 2 a and acommon wiring 3 are formed out of a first metal layer. There upon, withan insulating layer 11 a in between, the source wiring 7, a drainelectrode 6 and the second pixel electrode 1 b are formed out of asecond metal layer. There upon, with an insulating layer 11 b inbetween, the first pixel electrode 1 a, the second opposing electrode 2b and the storage capacitor electrodes 10 d, 10 e are formed of atransparent electric conductor layer. The first pixel electrode 1 a isconnected to the drain electrode 6 through a contact hole 13. The secondopposing electrode 2 b is connected to the common wiring 3 through acontact hole 14.

[0182] In this structure, when a positive voltage is applied to dots D1and D2, in the left dot D1, the transparent first pixel electrode 1 ahas a relatively positive electric potential, and, in the right dot D2,the transparent second opposing electrode 2 b has a relatively negativeelectric potential. When a negative voltage is applied to dots D1 andD2, in the left dot D1, the transparent first pixel electrode 1 a has arelatively negative electric potential, and, in the right dot D2, thetransparent second opposing electrode 2 b has a relatively positiveelectric potential. Thereby, the flicker polarities are cancelledbetween the two dots D1 and D2.

[0183] In the display device of the present embodiment, in order tofurther enhance the flicker reduction effect, bringing the flickerpolarities of the two dots D1 and D2 into balance is desirable. For thatpurpose, it is desirable that the capacities of the two storagecapacitor electrodes 10 d, 10 e be made equal and it is advantageousthat the two storage capacitor electrodes 10 d, 10 e be designed to beformed out of the same material, thereby making the areas of the twostorage capacitor electrodes equal. In the right subdot SD2 of thepresent embodiment, as shown in FIG. 24(c), the transparent second pixelelectrode 1 b makes a connection between layers and the storagecapacitor electrode 10 e is made of a transparent electric conductor. Asa result, the design period of the TFT array is shortened withoutadversely affecting the design, enhancing the manufacturing yield byusing a design having a high tolerance for the errors introduced by themanufacturing process. As in Embodiment 5, storage capacitor electrodes10 d, 10 e can also be formed on the gate wiring 4 out of a metal layer.

[0184] (Embodiment 10)

[0185]FIG. 25 is a plan view showing the structures of two adjacent dotson an array substrate in a display device according to Embodiment 10 ofthe invention. FIGS. 26(a), 26(b) and 26(c) are sectional views of FIG.25 taken along the lines AA-AA′, BB-BB′ and CC-CC′.

[0186] In the display device of Embodiment 9, the storage capacitorelectrodes 10 d, 10 e are formed on the gate wiring 4. On the otherhand, in the display device of the present embodiment, storage capacitorelectrodes 10 b, 10 c are formed on a common wiring 3. In FIGS. 25,26(a), 26(b) and 26(c), those elements which are identical to theelements of Embodiment 9 are identified with the same numerical symbols,and repetitious explanation will be omitted.

[0187] As shown in FIGS. 25, 26(a), 26(b) and 26(c), on an arraysubstrate 9, a gate wiring 4, a first opposing electrode 2 a and acommon wiring 3 are formed out of a first metal layer. There upon, withan insulating layer 11 a in between, a source wiring 7, a drainelectrode 6, a second pixel electrode 1 b and storage capacitorelectrodes 10 b, 10 c are formed out of a second metal layer. Thereupon, with an insulating layer 11 b. in between, a first pixel electrode1 a and a second opposing electrode 2 b are formed of a transparentelectric conductor layer. The first pixel electrode 1 a is connected tothe storage capacitor electrode 10 b through a contact hole 13. Thesecond opposing electrode 2 b is connected to the common wiring 3through a contact hole 14.

[0188] Like that in Embodiment 9, in the display device of the presentembodiment, flicker polarities are cancelled between the two adjacentdots D1 and D2. The present embodiment has a distinctive feature in thatan uniform display with a reduced distortion of scanning voltage can beobtained even on a wide screen because its additional capacitance of thegate wiring 4 is reduced.

[0189] Like in Embodiment 9, in the display device of the presentembodiment, in order to further enhance the flicker reduction effect,bringing the flicker polarities of the two dots D1, D2 into balance isdesirable. For that purpose, it is desirable that the capacities of thetwo storage capacitor electrodes 10 b, 10 c be made equal and it isadvantageous that the two storage capacitor electrodes 10 b, 10 c bedesigned to be formed of the same material, thereby making the areas ofthe two storage capacitor electrodes equal. In the left D1 of thepresent embodiment, the transparent first pixel electrode 1 a makes aconnection between layers and the storage capacitor electrode 10 b isformed out of a metal layer. As a result, the design period of the TFTarray is shortened without adversely affecting the design, enhancing themanufacturing yield by using a design having a high tolerance for theerrors introduced by the manufacturing process. Like in Embodiment 9,the storage capacitor electrodes 10 b, 10 c can also be formed on thecommon wiring 3 out of a transparent electric conductor layer.

[0190] (Embodiment 11)

[0191] The present embodiment relates to color display devices withstructures as describe in the above embodiments of the presentinvention. In a color display device having dots arranged in a matrix, ablack matrix and a color filter are generally formed in an opposingsubstrate facing an array substrate. The color filter is formed on anaperture of the black matrix, and each pixel thereof has a color layerof red, green or blue so that, in the display device as a whole, thesethree colors are repeated in an array. In other words, as shown in thearea enclosed by the bold line in FIG. 27, it is common that one pixel91 is formed out of three dots each having one of three primary colors,i.e, red (R), green (G) and blue (B).

[0192] As shown in FIG. 28, this color display device comprises ascanning signal driver M1 supplying a scanning signal by applying aprescribed voltage to a gate wiring 4 and an image signal driver M2supplying an image signal by applying a prescribed voltage to a sourcewiring 7. These drivers M1, M2 are controlled by a controller C. In thecolor display device having such structure, a bright image with a wideviewing angle and reduced flicker can be obtained by arranging each dotshown in FIG. 27 so as to have a structure as described in the aboveembodiments of the invention.

[0193] (Embodiment 12)

[0194] The present embodiment relates to a color display device inwhich, in the dot array on an array substrate shown in FIG. 27, threedots (RGB) in one pixel are structured so as to have the same structureand flicker polarities are cancelled between any two adjacent pixels.FIG. 29 shows dot arrays in the two adjacent pixels.

[0195] In FIG. 29, dots P and Q are structured so that they have flickerpolarities opposite of each other relative to the same drive voltage.For example, the structure of dot D1 in Embodiments 9 and 10 correspondsto that of P and the structure of dot D2 corresponds to that of Q. Thesubscripts R, G and B express the colors of each dot. According to thepresent embodiment, as shown in the figure, in the two adjacent pixels91, 91, the structure of the dots is the same within a pixel anddifferent from that of the dots in the adjacent pixel. This makes itpossible to readily cancel flicker polarities between any two adjacentpixels. Furthermore, since the dots within a pixel have the sameproperties, this arrangement has an advantage that color distortion canbe prevented even in halftone display which tends to be adverselyaffected by the difference between the brightness and voltageproperties.

[0196] (Embodiment 13)

[0197] In the color display device of Embodiment 12, the dots have thesame structure within a pixel. On the other hand, as shown in FIG. 30,in a color display device according to the present embodiment, any twoadjacent dots are arranged so as to have different structures. Thereby,flicker polarities can be cancelled between more subdivided regions.

[0198] (Embodiment 14)

[0199] The present embodiment relates to a color display device havingthe dot array as shown in FIG. 29 which employs a drive method furtherenhancing the flicker reduction effect.

[0200] In order to reduce flicker, it is preferable that the arrangementcycle of the regions showing the same flicker polarity relative to asame voltage differ from the inversion cycle of a driving voltage. Ifthe two cycles are coincident with each other, the effect of inversionis offset, adversely affecting the flicker reduction effect.

[0201] Next, examples of the repeated patterns of dots (array of P and Qin FIG. 29) and desirable combinations with the inversion methods of adrive voltage will be explained. FIGS. 31(a) to 31(f) show, when it isassumed, as shown in FIG. 29, that the dots within a pixel 91 have thesame structure as in, the polarities of the drive wave in an odd frame,the dot structure and the patterns of flicker polarity (odd frame)defined by their combination. Although not shown in the figures, an evenframe has a pattern of drive wave polarity inverted from that of an oddframe, resulting in a pattern of flicker polarity opposite to that of anodd frame.

[0202] An enhanced flicker reduction effect can be obtained in anarrangement in which the distribution of flicker polarity of pixels ordots is inverted every line.

[0203] Specific examples of such combinations are as follows:

[0204]FIG. 31(a): Combination of a line-inversion (row-inversion) driveand a line-non-inversion (row-non-inversion) dot array;

[0205]FIG. 31(c): Combination of a frame-inversion drive and aline-inversion (row-inversion) dot array; and

[0206]FIG. 31(e): Combination of a column-inversion drive and aline-inversion (row-inversion) dot array.

[0207] On the other hand, for example, when a checkerboard patternappears on a computer screen as wallpaper, etc., it is preferable that,between the pixels or dots, flicker polarity be inverted every two linesto prevent interference between the checkerboard pattern and the flickerpattern. Specific examples of such combinations are as follows:

[0208]FIG. 31(b): Combination of a line-inversion (row-inversion) driveand a two-line-inversion (two-row-inversion) dot array;

[0209]FIG. 31(d): Combination of a frame-inversion drive and atwo-line-inversion (two-row-inversion) dot array; and

[0210]FIG. 31(f): Combination of a column-inversion drive and atwo-line-inversion (two-row-inversion) dot array.

[0211] Although not shown, as a pattern in which flicker polarityinversion between the pixels or dots is performed every two lines,regarding drive wave polarity and dot structure, it is also possible toswitch the pattern of the drive inversion cycle and the dot arrangementcycle shown in FIGS. 31(b) and 31(f). Specific examples are as follows:

[0212] (b′): Combination of a two-line-inversion (two-row-inversion)drive and a line-inversion (row-inversion) dot array; and

[0213] (f′): Combination of a two-line-inversion (two-row-inversion)drive and a column-inversion dot array.

[0214] Likewise, when n is 3 or greater, it is possible to invertflicker polarities between pixels and dots every n lines. When n is 10or smaller (preferably 5 or smaller), interference with checkerboardpatterns can be prevented while reducing flicker, obtaining the sameeffect achieved by inverting flicker polarity distribution every twolines

[0215] (Embodiment 15)

[0216] The present embodiment relates to a color display device havingthe dot array shown in FIG. 30 in which employs a drive method furtherenhancing the flicker reduction effect.

[0217] In order to reduce flicker, like in Embodiment 14, it ispreferable that the arrangement cycle of the regions showing the sameflicker polarity relative to a same voltage differ from the inversioncycle of a driving voltage.

[0218] Next, examples of the repeated patterns of dots (array of P and Qin FIG. 30) and desirable combinations with the inversion methods of adrive voltage will be explained. FIGS. 32(a) to 32(d) show, when assumedthe two adjacent dots have the different structures in within pixel 91as shown in FIG. 30, polarities of drive wave in an odd frame, the dotarray and patterns of flicker polarity (odd frame) defined by theircombination. Although not shown in the figure, an even frame has apattern of drive wave polarity inverted to that of an odd frame,resulting in having a pattern of flicker polarity inverted to that of anodd frame.

[0219] Like in Embodiment 14, an enhanced flicker reduction effect canbe obtained in an arrangement in which the distribution of flickerpolarity of pixels or dots is inverted every line.

[0220] Specific examples of such combinations are as follows:

[0221]FIG. 32(a): Combination of a line-inversion (row-inversion) driveand a line-non-inversion (row-non-inversion) dot array; and

[0222]FIG. 32(c): Combination of a frame-inversion drive and aline-inversion (row-inversion) dot array.

[0223] On the other hand, for example, when a checkerboard patternappears on a computer screen as a wallpaper, etc., it is preferablethat, between the pixels or dots, flicker polarity be inverted every twolines to prevent interference between the a checkerboard pattern and theflicker pattern. Specific examples of such combinations are as follows:

[0224]FIG. 32(b): Combination of a line-inversion (row-inversion) driveand a two-line-inversion (two-row-inversion) dot array; and

[0225]FIG. 32(d): Combination of a frame-inversion drive and atwo-line-inversion (two-row-inversion) dot array.

[0226] Although not shown, as a pattern in which flicker polarityinversion between the pixels or dots is performed every two lines,regarding drive wave polarity and dot structure, it is also possible toswitch the pattern of the drive inversion cycle and the dot arrangementcycle in FIG. 32(b). Specific examples are as follows:

[0227] (b′): Combination of a two-line-inversion (two-row-inversion)drive and a line-inversion (row-inversion) dot array.

[0228] Likewise, when n is 3 or greater, it is possible to invertflicker polarities between pixels and dots every n lines. When n is 10or smaller (preferably 5 or smaller), interference with checkeredpatterns can be prevented while reducing flicker, obtaining the sameeffect achieved by inverting flicker polarity distribution every twolines.

[0229] The display devices according to Embodiments 14 and 15 can beoperated in the same manner as shown in FIG. 28 described above. Thisallows a display of bright images with wide viewing angles and reducedflicker, when considering the entire screen or the regions comprising aplurality of dots as a whole.

[0230] In Embodiments 14 and 15, the relationship between the drive wavepolarity and the dot array are explained with a dot taken as the unit;however, the preferable combinations of the drive wave polarity and thedot array described in the embodiments can also achieve the same effectswhen a pixel is assumed to be the unit. Furthermore, it is also possibleto consider the drive wave polarity or the dot array with a dot as theunit and the other with a pixel as the unit.

[0231] (Embodiment 16)

[0232]FIG. 33(a) is a sectional view of the display device according toEmbodiment 16 and FIG. 33(b) is a plan view showing the structure of onedot of the array substrate. FIG. 33(a) is a view taken along the lineDD-DD′ in FIG. 33(b).

[0233]FIG. 34 is an expanded sectional view showing the structure arounda switching element of a display device according to the presentembodiment.

[0234]FIG. 35(a) is a plan view showing a 4×4 dot section of pixels andFIGS. 35(b) and 35(c) are schematic diagrams showing the polaritiescreated in the pixels. In FIG. 35(a), S1, S2, etc. indicate imagesignals supplied to each pixel and G1, G2, etc. indicate scanningsignals supplied to each pixel.

[0235] In FIG. 33, 201 represents an opposing substrate, 202 representsliquid crystal, 209 a represents an oriented film formed inside of thearray substrate 9, 209 b represents an oriented film formed inside ofthe opposing substrate 201, and 210 a, 210 b and 210 c represent colorfilter materials. Other elements which are identical to the elements ofEmbodiment 1 are identified with the same numerical symbols, andrepetitious explanation will be omitted. In the present embodiment, apixel electrode 1 is formed out of a metal material and an opposingelectrode 2 is formed of a transparent electric conductor.

[0236] In FIG. 34, 8a represents an a-Si layer, 8 b represents an n+type a-Si layer and 14 represents a contact hole formed in insulatinglayers 11 a, 11 b.

[0237] The display device of the present embodiment is formed in themanner described below. On the array substrate 9, a first metal layer isformed of an opaque electric conductor made of Al, Ti or the like. Thefirst metal layer is patterned into predetermined shapes to obtain acommon wiring 3 and a gate wiring 4. On the thus obtained layer, theinsulating layer 11 a is formed, and then, a semiconductor switchingelement 5 is formed out of the a-Si layer 8 a and the n+ type a-Si layer8 b on the predetermined area of the insulating layer 11 a. Thereafter,on the predetermined areas of the insulating layer 11 a and thesemiconductor switching element 5, a second metal layer is formed out ofan opaque electric conductor made of Al, Ti or the like, and then thesecond metal layer is patterned into predetermined shapes to obtain asource wiring 7, a drain electrode 6 and a pixel electrode 1. On thethus obtained layer, the insulating layer 11 b made of SiNx or the likeis formed. The insulating layer 11 b also serves as an overcoatprotecting the semiconductor switching element 5.

[0238] Thereafter, the opposing electrode 2 is formed out of an ITOfilm, which is a transparent electric conductor. In order to make thecommon wiring 3 made of an opaque electric conductor and the opposingelectrode 2 made of a transparent electric conductor electricallyconductive, a contact hole 14 is formed in the insulating layers 11 a,11 b.

[0239] Then, on the array substrate 9 and the opposing substrate 201,oriented films 209 a, 209 b made of polyimide or the like are formed toalign molecules of liquid crystal 202.

[0240] The opposing substrate 201 is arranged so as to face the arraysubstrate 9. On the opposing substrate 201, the red color filtermaterial 210 a, the green color filter material 210 b, the blue colorfilter material 210 c and a black matrix 211 are formed so as to have apredetermined pattern.

[0241] The thus obtained array substrate 9 and opposing substrate 201have their orientation directions formed in predetermined directions.The substrates are bonded together on the edges by a sealer, and liquidcrystal 202 is sealed therein.

[0242] Operation of the display device is described below. Thesemiconductor switching element 5 has its on-and-off status controlledby drive signals supplied from the gate wiring 4. Then, an electricfield is generated by a liquid crystal drive voltage applied between thepixel electrode 1 and the opposing electrode 2; which are both connectedto the semiconductor switching element 5. By varying the orientationdirections of the liquid crystal 202, the brightness (lighttransmittance) of each pixel is controlled to achieve image formation.

[0243] In FIG. 33, d represents the cell gap, w1 represents the wiringwidth of the opposing electrode 2, w2 represents the wiring width of thepixel electrode 1 and 1 represents the distance between the opposingelectrode 2 and the pixel electrode 1.

[0244] In the present embodiment, as shown in FIG. 33, it is assumedthat the wiring width of the opposing electrode 2 is 5 μm (w1=5 μm), thewiring width of the pixel electrode 1 is 4 μm (w2=4 μm), the cell gap is4 μm (d=4 μm) and the distance between the electrodes is 10 μm (1=10μm). In other words, it is designed so that the wiring widths of theopposing electrode 2 and the pixel electrode 1 (w1, w2) becomeapproximately the same as the distance between the array substrate 9 andthe opposing substrate 201, i.e., d (cell gap).

[0245] Regarding the shape of the electrode, for example, as shown inFIG. 33(b), preferable is a comb-like electrode in which the opposingelectrode 2 and the pixel electrode 1 are alternately arranged with alateral electric field generated between the opposing electrode 2 andthe pixel electrode 1. By employing the above described electrodearrangement, in addition to the lateral electric field, the peripheralelectric fields of the individual electrodes 1, 2 enhance the electricfield strength on the electrodes, rotating the liquid crystal. In thepresent embodiment, by forming the pixel electrode 2 out of atransparent conductive material, the electrode transmits light.

[0246] According to such an electrode structure, for example, byemploying the liquid crystal 202 described below, it is possible tosupply sufficient electric field strength and drive the liquid crystalusing a generally applied liquid crystal drive voltage (around 5V).

[0247] Specifically, as a liquid crystal material 202, a cyano-basedliquid crystal material containing a cyano-based compound in the rangefrom about 10% to about 20% is used. Here, the optical-path differenceΔn×d (multiply the cell gap d by the difference in the refractive indexΔn) is assumed to be around 350 nm. It is also assumed that the liquidcrystal material used in the liquid crystal layer 2 have a splay elasticconstant K11 of 12 pN (K11=12 pN), a twist elastic constant K22 of 7 pN(K22=7 pN), a bend elastic constant K33 of 18 pN (K33=18 pN) and adielectric constant anisotropy Δe of +8 (Δe=+8). The dielectric constantanisotropy Δe and the bend elastic constant K33 are important factors inselecting the drive voltage applied to the liquid crystal. To lower thevoltage, it is preferable that the dielectric constant anisotropy Δe be+8 or greater and the bend elastic constant K33 be 18 pN or smaller.Cyano-based compounds are useful to prevent the localized accumulationof electric charge in the liquid crystal; however, having aconcentration thereof exceeding 35% may lower the reliability of thedevice because the ionicity is too strong.

[0248] Furthermore, since the pixel electrode 1 and the opposingelectrode 2 are crooked, the liquid crystal molecules rotate in twodirections. Therefore, differences in color observed from differentviewing angles can be eliminated, obtaining a panel structure exhibitinglittle variance in color when seen from variable directions. Not shownin the figure, however, if the source wiring 7 and the black matrix 211are formed into crooked shapes having the same crooking angles as theopposing electrode 2 and the pixel electrode 1, the increase in areawhich blocks light caused by the crooked shapes of the electrodes 1, 2can be offset, obtaining a liquid crystal display device exhibiting afurther enhanced aperture ratio.

[0249] The advantages achieved by the display device of the presentembodiment will be described below. FIGS. 36(a) and 36(b) show the lighttransmittance properties of a pixel portion in a display deviceaccording to the present embodiment. In this figure, the pixelelectrodes (opaque) 1, 1, the opposing electrode (transparent) 2 and therelative brightness distribution (transmittance distribution) in theaperture are shown. FIG. 36(a) shows the case where a positive imagesignal is applied to the pixel electrode 1 and FIG. 36(b) shows the casewhere a negative image signal is applied to the pixel electrode 1. Fromthe figures, it is understood that the light transmittance propertiesare changed by the polarities of the liquid crystal drive voltage,causing flicker polarity (light or dark polarity). As described above,the light transmittance properties are changed by the polarities of theliquid crystal drive voltage, and therefore the frame-inversion drivewhereby the polarity is inverted every frame causes flicker. In theH-line inversion drive in which a drive voltage polarity is invertedevery line or the V-line inversion drive in which a drive voltagepolarity is inverted every column, when a specific pattern such as avertical line or a horizontal line is displayed, it appears on thescreen as vertical stripes or horizontal stripes.

[0250] Therefore, the drive method employed in the liquid crystaldisplay device of the present embodiment is the 1H/1V line-inversiondrive (also referred to as the dot inversion drive) in which thepolarity inversion of the pixel voltage is performed every line andevery column as shown in FIG. 35(b). As an alternative, the 2H/1Vline-inversion drive as shown in FIG. 35(c) in which polarity inversionof the pixel voltage is performed every two lines and every column canbe employed.

[0251] In the 1H/1V line-inversion drive shown in FIG. 35(b), when apattern of vertical lines or horizontal lines are displayed, thebrightness difference between the positive and negative polarities arecancelled between two adjacent pixels, and thereby apparent flicker canbe cancelled. On the other hand, when a checkerboard patter isdisplayed, the 2H/1V line-inversion drive shown in FIG. 35(c) ispreferable. According to this method, even in a checkerboard pattern,the brightness difference between the positive and negative polaritiescan be cancelled, and thereby flicker does not appear on the screen. Thesame effect can be achieved by employing the 1H/2V line-inversion drive.

[0252] In the present embodiment, inversion of drive voltage polarity isperformed with the dot taken as the unit; however, it is also possibleto perform inversion of the pixel voltage polarity in the manner asshown in FIG. 35(b) or FIG. 35(c) when a pixel composed of red, greenand blue dots is assumed to be the unit. This arrangement isadvantageous in that color distortion can be prevented even in halftonedisplay which tends to be adversely affected by the difference betweenthe properties of brightness and voltage, since the properties of eachdot in a pixel can readily be balanced.

[0253] The conventional drive frequency for a frame is 30 Hz; however,apparent flicker can be cancelled by applying a frequency of 60Hz, sinceeven if the brightness differences caused by polarities are generated,the human eye cannot recognize them at a frequency this high. This isalso true in other embodiments.

[0254] (Embodiment 17)

[0255]FIG. 37(a) is a sectional view of the display device according toEmbodiment 17. FIG. 33(b) is a plan view showing the structure of onedot of the array substrate. FIG. 37(a) is a view taken along the lineEE-EE′ in FIG. 37(b).

[0256]FIG. 38 is an expanded sectional view showing the structure arounda switching element of a display device according to the presentembodiment.

[0257]FIG. 39(a) is a plan view showing a 4×4 dot section of pixels andFIG. 39(b) is a schematic diagram showing the waveform of image signalapplied to each pixel shown in FIG. 39(a). In FIG. 39(a), S1, S2, . . .indicate image signals supplied to each pixel, S1′, S2′, indicatecompensated image signals supplied to each pixel and G1, G2, . . .indicate scanning signals supplied to each pixel.

[0258] In the present embodiment, both the pixel electrode 1 and theopposing electrode 2 are made of transparent electric conductors. Inother respects, the configuration thereof is the same as that of theEmbodiment 16. Therefore, the elements which are identical to theelements of Embodiment 16 are identified with the same numericalsymbols, and repetitious explanation will be omitted.

[0259] The display device of the present embodiment is formed in amanner as described below. On the array substrate 9, a first metal layeris formed out of an opaque electric conductor made of Al, Ti or thelike, and the first metal layer is patterned into predetermined shapesto obtain a common wiring 3 and a gate wiring 4. On the thus obtainedlayer, the insulating layer 11 a is formed and a semiconductor switchingelement 5 formed out of an a-Si layer 8 a and an n+ type a-Si layer 8 bis obtained on the predetermined area of the insulating layer 11 a.Thereafter, on the predetermined areas of the insulating layer 11 a andthe semiconductor switching element 5, a second metal layer is formedout of an opaque electric conductor made of Al, Ti or the like, and thenthe second metal layer is patterned into predetermined shapes to obtaina source wiring 7, a drain electrode 6 and a pixel electrode 1. On thethus obtained layer, the insulating layer 11 b made of SiNx or the likeis formed. The insulating layer 11 b also serves as an overcoatprotecting the semiconductor switching element 5.

[0260] Thereafter, on the insulating layer 11 b, the pixel electrode 1and the opposing electrode 2 are formed out of an ITO film, which is atransparent electric conductor. The opposing electrode 2 is connected tothe common wiring 3 through a contact hole 14 formed in the insulatinglayers 11 a, 11 b. The pixel electrode 1 is connected to the drainelectrode 6 through a contact hole 13 formed in the insulating layer 11b. Instead of forming the pixel electrode 1 and the opposing electrode 2on the same layer as in the present embodiment, it is also possible toprovide another layer and form the elecctrodes on separate layers.

[0261] Then subsequent production steps are the same as those ofEmbodiment 16. In the thus obtained display device of the presentembodiment, both the pixel electrode 1 and the opposing electrode 2 aretransparent, realizing a display device with an enhanced actual apertureratio compared to that of Embodiment 16.

[0262] The advantages achieved by the display device of the presentembodiment will be described below. FIGS. 40(a) and 40(b) show lighttransmittance properties of a pixel portion in a display deviceaccording to the present embodiment. In this figure, the pixelelectrodes (transparent) 1, 1, the opposing electrode (transparent) 2and the relative brightness distribution (transmittance distribution) inthe aperture are shown. FIG. 40(a) shows the case where a positive imagesignal is applied to the pixel electrode 1 and FIG. 40(b) shows the casewhere a negative image signal is applied to the pixel electrode 1. Fromthe figures, it is understood that the light transmittance propertiesare changed by the polarities of the liquid crystal drive voltage,causing flicker polarity (light or dark polarity). In FIG. 40, there aretwo pixel electrodes 1 and one opposing electrode 2. Therefore, even ifboth electrodes are transparent, the displayed images become brighter inthe case (b) where the pixel electrode 1 has a relatively negativevoltage. This phenomenon occurs because of the difference in numbers andareas between the pixel electrode 1 and the opposing electrode 2.

[0263] In the present embodiment, as shown in FIG. 39, the difference inbrightness between the positive and negative polarities can be cancelledby supplying brightness compensation signals S1′, S2, . . . in additionto general image signals S1, S2, . . . .Specifically, when a positiveliquid crystal drive voltage is applied to the pixel electrodes 1, 1, asshown in FIG. 39(b), compensation for the image signal is performed byadding brightness compensation signals +S1′, +S2′ . . . to image signalS1. Thereby, the variance in the electric potential of a liquid crystaldrive voltage is increased and the displayed image becomes brighter. Asa result, as shown in FIG. 40(a), the light transmittance propertychanges from the condition without brightness compensation signal,represented by the solid line, to the condition with brightnesscompensation signal, represented by the broken line.

[0264] On the other hand, when a negative liquid crystal drive voltageis applied to the pixel electrodes 1, 1, as shown in FIG. 39(b),compensation for image signal is performed by adding brightnesscompensation signals −S1′, −S2′ . . . to image signal S1. Thereby, thevariance in the electric potential of a liquid crystal drive voltage isdecreased and the displayed image becomes darker. As a result, as shownin FIG. 40(b), the light transmittance property changes from thecondition without brightness compensation signal represented by thesolid line to the condition with brightness compensation signalrepresented by the broken line.

[0265] By increasing or decreasing the transmittance properties bysupplying brightness compensation signals, the variances in brightnesswhen a positive liquid crystal drive voltage is applied and when anegative liquid crystal drive voltage is applied can be madeapproximately the same.

[0266] It is preferable that the brightness compensation signals S1′,S2′ . . . be controlled so that an appropriate voltage is supplied basedon the ratio of the area of between the pixel electrode 1 and theopposing electrode 2, which are both formed out of transparentconductive layers. Specifically, the variance in brightness caused bythe polarity of a liquid crystal drive voltage can be cancelled if thearea SA of the transparent pixel electrode and the area SB of thetransparent opposing electrode 2 are the same. When SA and SB aredifferent, the variance in brightness caused by polarity remains. Themore the ratio of SA to SB moves away from 1, the greater the variancein brightness is. Therefore, it is preferable that the variance inbrightness be cancelled by supplying an appropriate compensation voltageobtained based on a calculation of how far away the area ratio isfrom 1. Having this arrangement allows a flicker reduction by cancelingthe variance in brightness caused by polarities regardless of the numberof electrodes.

[0267] In the present embodiment, both the pixel electrode 1 and theopposing electrode 2 are transparent; however, even if only the opposingelectrode 2 is formed out of a transparent conductive layer like inEmbodiment 16, the same effect can be achieved by adding brightnesscompensation signals.

[0268] It is also true that in the present embodiment, like inEmbodiment 16, the flicker reduction effect can be enhanced by employingthe double-speed drive method which has a drive frequency of 60 Hz orhigher.

[0269] In Embodiment 16 and the present embodiment, a-Si (amorphoussilicon) is used for forming a semiconductor switching element 5;however, use of p-Si (polysilicon) or the other semiconductor layers canalso achieve a similar result. This is true also in the otherembodiments.

[0270] In Embodiment 16 and the present embodiment, there areexplanations of cases where the pixel electrode 1 and the opposingelectrode 2 are crooked; however, the actual aperture ratio can beenhanced regardless of the electrode shape, allowing use of linearelectrodes, U-shape electrodes or others. This is true also in the otherembodiments.

[0271] (Embodiment 18)

[0272] In the embodiments descried above, a rectangular dot was takenfor the example as the display unit, and the cases where the dots arearranged in matrix are explained. However, the advantage of the presentinvention is satisfactorily achieved even when a display unit is not arectangular dot or the display units are not arranged in matrix.

[0273] To be more specific, the present invention can be applied to astructure having elements whose functions are substantially the same asthose of a pixel electrode and an opposing electrode even if theelements are not called by such names. Such examples include acircular-graph-shaped indicator I as shown in FIG. 41 for use in severalkinds of meters and a segment display as shown in FIG. 42 for use indisplay of numerical characters or the like. By structuring each displayblock B and each segment SG based on the schemes described in theembodiments of the invention, it is possible to cancel flicker in theblocks B and the segments SG. As a result, an excellent display with awide viewing angle, satisfactory brightness and reduced flicker can beobtained.

[0274] Also in a liquid crystal display device having a differentarrangement, by structuring display units that perform the same kind ofdisplay based on the schemes described in the above embodiments, it ispossible to cancel flicker within each display unit. Thereby, anexcellent display with a wide viewing angle, satisfactory brightness andreduced flicker can be obtained.

[0275] Also in the case where the whole surface of a wide image iscontrolled by a single signal such as in shutters for lighting or blindsfor windows, with assuming it to be one display unit, by structuring thedisplay unit so as to have two flicker polarities based on the schemesdescribed in the embodiments of the invention, flicker can be cancelledin each display unit. This achieves light control with reduced flickerand without being affected by a variance in the observation direction.

[0276] (Other Embodiments)

[0277] In the display devices according to the embodiments describedabove, it is preferable that, in one dot, the total number of the pixelelectrodes 1 and the opposing electrodes 2 be an odd number and thenumber of intervals between the pixel electrodes 1 and the opposingelectrodes 2 be an even number. For example, in the structure ofEmbodiment 1 shown in FIG. 1 and that of Embodiment 5 shown in FIG. 5,by arranging the numbers of the electrodes and the intervalstherebetween as above, the composition of a dot becomes almostsymmetrical in the left and the right halves, the flicker reductioneffect can be enhanced. This is also true in the arrangements ofEmbodiment 9 shown in FIG. 25 and Embodiment 10 shown in FIG. 23.

[0278] In the arrangements of Embodiment 5 shown in FIG. 10 andEmbodiment 6 shown in FIG. 14, it is preferable that the number of theopposing electrodes disposed between the two source wirings be an oddnumber so that one of the opposing electrodes is situated in the middleof the two source wirings. Thereby, two dots can be separated by theopposing electrode, enhancing the aperture ratio.

[0279] In the arrangements of Embodiment 7 shown in FIG. 16 andEmbodiment 8 shown in FIG. 19, it is preferable that the total number ofopposing electrodes in the dot be an odd number, and it is morepreferable that the number be 5+4 n (n is an integer), i.e., 5 or 9,etc. This allows the composition of the dot to become almost symmetricalin the left and the right halves, enhancing the flicker reductioneffect.

[0280] In the embodiments descried above, IPS-style liquid crystaldisplay devices are used; however, as long as they have an arrangementcomprising a pixel electrode and an opposing electrode on one substrate,there is no limitation on the style of the liquid crystal display used.

[0281] Furthermore, with respect to the materials of the pixel electrodeand the opposing electrode, they are not limited to a combination of atransparent conductive layer and a metal layer. For example, a material,even one which is not completely transparent, if it exhibits atransmittance at a certain level, has the effect of improving thebrightness of the display device. Therefore, such a material and a metallayer can be used in combination. A combination of two transparentconductive layers having different transmittances is also possible. Thisarrangement can further enhance the transmittance.

[0282] When performing reflective-type display, the present inventioncan be employed in a display device comprising a combination of twomaterials having different reflectances or a display device having areflective electrode as a back side electrode and a transparentelectrode as an observer's side electrode.

[0283] In a liquid crystal display device, as described above, flickertends to occur in the case where some portion of an electric field has asplay-shape around an electrode, causing the flexoelectric effect, andthe case where electric fields become asymmetric in the left and rightelectrodes affected by a peripheral electric potential caused by someportion of a display unit having no electrode. The present inventionexhibits remarkable advantages compared to display devices having suchstructures.

[0284] An example of a display device having such a structure includes aliquid crystal display device in which liquid crystal is driven by anelectric field substantially parallel to a substrate. To be morespecific, an IPS-style liquid crystal display device in which liquidcrystal molecules respond only in the direction parallel to thesubstrate, an FFS (Fringe Field Switching) style liquid crystal displaydevice, and an HS (Hybrid Switching) style liquid crystal display deviceare included. The above-described structures of the embodiments of theinvention can be applied to a perpendicular-oriented type liquid crystaldisplay device, in which liquid crystal molecules L are perpendicularlyoriented as shown in FIG. 43(a) when a drive voltage is turned off andthe orientation angles of the liquid crystal molecules L change alongthe electric field generated between electrodes 21, 22 as shown in FIG.43(b) when the drive voltage is turned on.

[0285] In an MVA (Multi-domain VA) style liquid crystal device, asplay-shaped electric field is used when the orientation of the liquidcrystal is divided by the distortion of the electric field. Therefore,the arrangements of the present invention can be employed in areflective-type display or the like which uses electrodes havingdifferent optical properties.

[0286] Rod type low molecular weight compounds are generally used as theliquid crystal materials in each embodiment of the invention. In orderto obtain the desired properties, anywhere from a few to several dozenkinds of materials are mixed. There is no limitation on the materialsused; however, in order to reduce the flicker polarities, a mixturecontaining a compound having a wider end directed to the positiveelectrode side, which prevents the flexoelectric effect, is desirable.The compounds represented by general formulae (A) to (F) below arepreferable.

[0287] In the above general formulae (A) to (F), X and Y representcyclic hydrocarbon residues. Specific examples are aromatic hydrocarbonresidues (benzene ring), aliphatic hydrocarbon residues (cyclohexanering), and compounds in which some of the carbon atoms composingaromatic hydrocarbon residues or aliphatic hydrocarbon residues arereplaced by hetero atoms such as nitrogen or oxygen.

[0288] P represents central groups including ester groups (—COO—), etc.P includes something which directly connects the groups on both sides.

[0289] In the end groups, Cn can be F, CF₃, CHF₂ or CH₂F and CH₃ can beC_(n)H_(2n+1) (n is an integer from 2 to 20). These end groups areresponsible for changes in the properties of the liquid crystal such aselectric or optical anisotropy and the temperature in which it is arange forming liquid crystal.

[0290] The number of the cyclic groups contained in the core sectionenclosed by the broken line is three or less in practical applications;however, it can be greater than three.

[0291] As specific examples of the compounds described above, thecompounds represented the formula below are included.

1. A display device comprising: an array substrate; an opposing substrate facing the array substrate; and an electro-optic substance held between the array substrate and the opposing substrate, wherein the array substrate is provided with: a plurality of gate wirings and a plurality of source wirings intersecting each other; a pixel electrode disposed in each region defined by two adjacent gate wirings and two adjacent source wirings; a switching element for switching a voltage applied to the pixel electrode from the source wiring based on a signal voltage supplied from the gate wiring; a common wiring formed between the two adjacent gate wirings; and an opposing electrode being electrically connected to the common wiring and generating an electric field for driving the electro-optic substance between the opposing electrode and the pixel electrode whereto a voltage is applied, wherein the pixel electrode comprises a first pixel electrode and a second pixel electrode, and the opposing electrode comprises a first opposing electrode and a second opposing electrode, wherein a first region is formed in which an electric field is generated between the first pixel electrode and the first opposing electrode whose light transmittance is lower than that of the first pixel electrode, wherein a second region is formed in which an electric field is generated between the second pixel electrode and the second opposing electrode whose light transmittance is higher than that of the second pixel electrode.
 2. The display device according to claim 1, wherein the first region and the second region are adjacent to each other.
 3. The display device according to claim 1, wherein a voltage is supplied to the first pixel electrode and the second pixel electrode from the same source wiring based on a signal voltage fed from the same gate wiring.
 4. The display device according to claim 3, wherein the first region and the second region are formed in a single dot.
 5. The display device according to claim 4, wherein the interface between the first region and the second region is located on the common wiring, and the first pixel electrode is connected to the second pixel electrode and the first opposing electrode is connected to the second opposing electrode through contact holes formed in insulating layers held in between.
 6. The display device according to claim 4, wherein the source wiring is disposed between the first region and the second region, and the switching elements are arranged so as to correspond to the first pixel electrode and the second pixel electrode, respectively.
 7. The display device according to claim 4, wherein a plurality of the first regions and a plurality of the second regions are formed and alternately arranged along the gate wiring in such a manner that groups of two consecutively identical regions are alternately disposed, and the interface between that groups of two adjacent first regions and two adjacent second regions exists on the pixel electrode or the opposing electrode.
 8. The display device according to claim 1, wherein a plurality of the first regions and a plurality of the second regions are formed and arranged in a manner such that the flicker polarity cyclically changes along both the gate wiring and the source wiring based on the prescribed voltage polarity applied to the first pixel electrode and the second pixel electrode.
 9. The display device according to claim 8, wherein the flicker polarities are inverted at every dot along both the gate wiring and the source wiring.
 10. The display device according to claim 8, wherein the flicker polarities are inverted at every plurality of dots along both the gate wiring and the source wiring.
 11. The display device according to claim 1, wherein the first region and the second region each corresponds to a dot.
 12. The display device according to claim 1, wherein the first region and the second region each corresponds to a pixel composed of three dots of red, green and blue.
 13. The display device according to claim 1, further comprising storage capacitor electrodes electrically connected to the first pixel electrode and the second pixel electrode, each of the storage capacitor electrodes is arranged in the first region and the second region, wherein the two storage capacitor electrodes are located on the common electrode or the gate wiring with an insulating layer or insulating layers in between to form storage capacitor regions and the two storage capacitor regions have substantially the same capacity.
 14. The display device according to claim 13, wherein the two storage capacitor electrodes are made of the same material and have substantially the same surface area.
 15. The display device according to claim 1, wherein the first pixel electrode and the second opposing electrode are made of a transparent material and the first opposing electrode and the second pixel electrode are made of an opaque material.
 16. The display device according to claim 1, wherein the area of the first pixel electrode in the aperture of the first region and the area of the second opposing electrode in the aperture of the second region are substantially the same.
 17. The display device according to claim 16, wherein the first pixel electrode and the second opposing electrode have substantially the same transmittance.
 18. The display device according to claim 16, wherein an opaque layer is formed on the opposing substrate for blocking light over some portion of the array substrate and some portion of the first pixel electrode or the second opposing electrode is covered with the opaque layer.
 19. The display device according to claim 1, wherein drive voltages applied to the first region and the second region have the same polarity.
 20. The display device according to claim 1, wherein the first region and the second region have substantially the same absolute value of brightness difference between the case where the pixel electrode has a positive electric potential relative to the opposing electrode and the case where the pixel electrode has a negative electric potential relative to the opposing electrode.
 21. A display device comprising: an array substrate; an opposing substrate facing the array substrate; and an electro-optic substance held between the array substrate and the opposing substrate, wherein the array substrate is provided with: a plurality of gate wirings and a plurality of source wirings intersecting each other; a pixel electrode disposed in each region defined by two adjacent gate wirings and two adjacent source wirings; a switching element for switching a voltage applied to the pixel electrode from the source wiring based on a signal voltage supplied from the gate wiring; a common wiring formed between the two adjacent gate wirings; an opposing electrode being electrically connected to the common wiring and generating an electric field for driving the electro-optic substance between the opposing electrode and the pixel electrode whereto a voltage is applied; and an intermediate electrode disposed between the pixel electrode and the opposing electrode, wherein the intermediate electrode has a transmittance either higher or lower than both the pixel electrode and the opposing electrode.
 22. The display device according to claim 21, wherein the pixel electrode and the opposing electrode are formed out of the same material, and the intervals between the pixel electrode and the intermediate electrode and between the intermediate electrode and the opposing electrode are substantially the same.
 23. The display device according to claim 21,. wherein the intermediate electrode is resistively connected to the pixel electrode and the opposing electrode.
 24. The display device according to claim 21, wherein the intermediate electrode is subjected to capacity coupling with the pixel electrode and the opposing electrode.
 25. The display device according to claim 21, wherein the electric potential of the intermediate electrode becomes the average value of the electric potential of the pixel electrode whereto a voltage applied and the electric potential of the opposing electrode which functions as a standard electric potential.
 26. The display device according to claim 1 or 21, wherein the electro-optic substance is liquid crystal.
 27. The display device according to claim 26, wherein an alternating voltage is applied to the pixel electrode.
 28. A method of driving a display device having: an array substrate; an opposing substrate facing the array substrate; and an electro-optic substance held between the array substrate and the opposing substrate, the array substrate being provided with: a plurality of gate wirings and a plurality of source wirings intersecting each other; a pixel electrode disposed in each region defined by two adjacent gate wirings and two adjacent source wirings; a switching element for switching a voltage applied to the pixel electrode from the source wiring based on a signal voltage supplied from the gate wiring; a common wiring formed between the two adjacent gate wirings; and an opposing electrode being electrically connected to the common wiring and generating an electric field for driving the electro-optic substance between the opposing electrode and the pixel electrode whereto a voltage is applied, the pixel electrode and the opposing electrode being made of the materials having different transmittances, said method comprising the step of inverting the voltage applied to the pixel electrode for every predetermined adjacent region.
 29. The method of driving a display device according to claim 28, wherein the predetermined regions are adjacent to each other in two directions, along the gate wiring and the source wiring.
 30. The method of driving a display device according to claim 28, wherein each predetermined region corresponds to a dot.
 31. The method of driving a display device according to claim 28, wherein the predetermined region corresponds to two dots adjacent in a direction either along the gate wiring or the source wiring.
 32. The method of driving a display device according to claim 28, wherein the predetermined region corresponds to a pixel composed of three dots of red, green and blue.
 33. The method of driving a display device according to claim 28, wherein the predetermined region corresponds to two pixels each composed of three dots of red, green and blue, adjacent in a direction either along the gate wiring or the source wiring.
 34. A method of driving a display device having: an array substrate; an opposing substrate facing the array substrate; and an electro-optic substance held between the array substrate and the opposing substrate, the array substrate being provided with: a plurality of gate wirings and a plurality of source wirings intersecting each other; a pixel electrode disposed in each region defined by two adjacent gate wirings and two adjacent source wirings; a switching element for switching a voltage applied to the pixel electrode from the source wiring based on a signal voltage supplied from the gate wiring; a common wiring formed between the two adjacent gate wirings; and an opposing electrode being electrically connected to the common wiring and generating an electric field for driving the electro-optic substance between the opposing electrode and the pixel electrode whereto a voltage is applied, the pixel electrode and the opposing electrode being made of the materials having different transmittances, said method comprising the step of inverting the voltage applied to the pixel electrode by increasing or decreasing the volume of prescribed brightness compensation voltage.
 35. A method of driving a display device having: an array substrate; an opposing substrate facing the array substrate; and an electro-optic substance held between the array substrate and the opposing substrate, the array substrate being provided with: a plurality of gate wirings and a plurality of source wirings intersecting each other; a pixel electrode disposed in each region defined by two adjacent gate wirings and two adjacent source wirings; a switching element for switching a voltage applied to the pixel electrode from the source wiring based on a signal voltage supplied from the gate wiring; a common wiring formed between the two adjacent gate wirings; and an opposing electrode being electrically connected to the common wiring and generating an electric field for driving the electro-optic substance between the opposing electrode and the pixel electrode whereto a voltage is applied, the pixel electrode and the opposing electrode being made of transparent electric conductors, the total area of the pixel electrode and the total area of the opposing electrode occupying the transparent portions in the regions being different from each other, said method comprising the step of inverting the voltage applied to the pixel electrode by increasing or decreasing the volume of prescribed brightness compensation voltage.
 36. A method of driving a display device having: an array substrate; an opposing substrate facing the array substrate; and an electro-optic substance held between the array substrate and the opposing substrate, the array substrate being provided with: a plurality of gate wirings and a plurality of source wirings intersecting each other; a pixel electrode disposed in each region defined by two adjacent gate wirings and two adjacent source wirings; a switching element for switching a voltage applied to the pixel electrode from the source wiring based on a signal voltage supplied from the gate wiring; a common wiring formed between the two adjacent gate wirings; and an opposing electrode being electrically connected to the common wiring and generating an electric field for driving the electro-optic substance between the opposing electrode and the pixel electrode whereto a voltage is applied, the pixel electrode comprising a first pixel electrode and a second pixel electrode, and the opposing electrode comprising a first opposing electrode and a second opposing electrode, a plurality of first regions generating an electric field between the first pixel electrode and the first opposing electrode having a lower light transmittance than the first pixel electrode being formed, a plurality of second regions generating an electric field between the second pixel electrode and the second opposing electrode having a higher light transmittance than the second pixel electrode being formed, said method comprising a step of inverting a voltage applied to the first pixel electrode and the second pixel electrode based on the arrangement cycles of the first region and the second region so as to flicker polarities cyclically change along both the gate wiring and the source wiring.
 37. The method of driving a display device according to claim 36, wherein said step of inverting the voltage comprises the step of inverting the flicker polarities at every dot along both the gate wiring and the source wiring.
 38. The method of driving a display device according to claim 36, wherein said step of inverting the voltage comprises the step of inverting the flicker polarities at every plurality of dots along one or both of the gate wiring and the source wiring.
 39. The method of driving a display device according to claim 28, 34, 35 or 36, wherein the driving frequency of the voltage applied to the pixel electrode is 60Hz or higher. 